Posted on by Tammy Plotner

Weekly SkyWatcher’s Forecast: October 8-14, 2012

Messier 73 - Credit: Palomar Observatory, courtesy of Caltech

Greetings, fellow SkyWatchers! With early evening dark skies, this is a perfect opportunity to take on some more serious studies. We’ll start off BIG… and work down to the really small. (Think Hickson Compact Groups.) There’s even a meteor shower this week! Now, get out your telescopes and get ready, cuz’ I’m waitin’ in the backyard and lookin’ for the “Double Dark”…

Monday, October 8 – Today marks the birthday of Ejnar Hertzsprung. Born 1873, Hertzsprung was a Danish astronomer who first proved the existence of giant and dwarf stars in the early 1900s. His discoveries included the relationship between color and luminosity, which wasn’t truly recognized until it was recovered by Henry Russell. Now it is a familiar part of all our studies as the Hertzsprung-Russell diagram. His use of absolute magnitudes will come into play tonight as we have a look at the age-old mystery of M73.

Located about three fingerwidths north-northwest of Theta Capricorni (RA 58.9 Dec -12 38), this 9th magnitude open cluster consisting of four stars was discovered by Charles Messier on October 4, 1780. He described it as a “Cluster of three or four small stars, which resembles a nebula at first glance…” Hotly debated as to whether or not the grouping is a genuine cluster or simply an asterism, it was also included in J. Herschel’s catalog (GC 4617) and given the NGC 6994 designation by Dreyer. In 1931 Collinder cataloged M73 as Cr 426, with an estimated distance of 12,000 light-years. Still, the debate about its authenticity as a physically related group continued.

At least two stars show the same proper motion, leading scientists to believe M73 may be the remnant of a much older and now dispersed cluster – or simply two related stars. Of the 140 stars investigated in the region, 24 may be real members, including those in Messier’s original observation. Thanks to the work of Hertzsprung and Russell, these candidates fall within the color-magnitude diagram of a 2 to 3 billion year old cluster with Messier’s suspect four being evolved giants. The most recent data indicates M73 may simply be an asterism – sharing no common proper motion, but until more studies are undertaken you can enjoy this unusual Messier in even a small telescope!

Tuesday, October 9 – Tonight is the peak of the Draconid meteor shower whose radiant is near the westering constellation of Hercules. This particular shower can be quite impressive when comet Giacobini-Zinner passes near Earth. When this happens, the fall rate jumps to 200 per hour and has even been known to reach 1000. So what am I going to tell you about this year? Comet Giacobini-Zinner reached perihelion on July 2nd of 2005, passing with 8 million kilometers of Earth, but has now greatly distanced itself from our solar system. Chances are the Draconids will only produce around 3 to 5 per hour, but no one knows for sure!

While we’re out, let’s take the time to have a peek at M72, just about a degree and a half west (RA 20 53.5 Dec -12 32) of last night’s target M73.

Originally found by Mechain on the night of August 29-30, 1780, this class IX globular cluster is one of the faintest and most remote of the Messiers, and Charles didn’t catalog it until over a month after its discovery. At around magnitude 9, this 53,000 light-year distant globular will be not much more than a faint round smudge in smaller aperture, but will take on a modicum of resolution in larger telescopes. Well beyond the galactic center and heading toward us at 255 kilometers per second, M72 is home to 42 variables and the average magnitude of its members is around 15. While mid-sized scopes will pick up a graininess in the texture of this globular, notice how evenly the light is distributed, with little evidence of a core region. Be sure to write down your observations!

Wednesday, October 10 – Today in 1846, William Lassell was busy at his scope as he made a new discovery – Neptune’s moon Triton! Although our everyday equipment can’t “see” Triton, we can still have a look at Neptune which is also hanging out in tonight’s study constellation of Capricornus. Try checking astronomy periodicals or many great on-line sites for accurate locator charts.

Tonight let’s head to the eastern portion of Capricornus and start by identifying Zeta about a fistwidth southwest of the eastern corner star – Delta. Now look southeast about 2 fingerwidths and identify 5th magnitude star 41. About one half degree west is our target we’ll be revisiting this evening, M30 (Right Ascension: 21 : 40.4 – Declination: -23 : 11).

At near magnitude 8, this class V globular cluster is well suited to even binoculars and becomes spectacular in a telescope. Originally discovered by Messier in August 1764 and resolved by William Herschel in 1783, some of M30?s most attractive features are the branches of stars which seem to radiate from its concentrated core region. Estimated to be around 26,000 light-years away, you’ll find it fairly well resolved in large aperture, but take time to really look. The dense central region may have already undergone core collapse – yet as close as these stars are, very few have collided to form x-ray binaries. For the smaller scope, notice how well M30?s red giants resolve and be sure to mark your notes!

Thursday, October 11 – Tonight is time for a telescopic challenge – a compact galaxy group. You’ll find it less than half a degree southeast of stellar pair 4 and 5 Aquarii (RA 20 52 26.00 Dec -05 46 19.1).

Known as Hickson 88, this grouping of four faint spiral galaxies is estimated to be around 240 million light-years away and is by no means an easy object – yet the galactic cores can just be glimpsed with mid-sized scopes from a very dark site. Requiring around 12.5? to study, you’ll find the brightest of these to be northernmost NGC 6978 and NGC 6977. While little detail can be seen in the average large backyard scope, NGC 6978 shows some evidence of being a barred spiral, while NGC 6977 shows the even appearance of a face-on. Further south, NGC 6976 is much smaller and considerably fainter. It is usually caught while averting and studying the neighborhood. The southernmost galaxy is NGC 6975, whose slender, edge-on appearance makes it much harder to catch.

Although these four galaxies seem to be in close proximity to one another, no current data suggests any interaction between them. While such a faint galaxy grouping is not for everyone, it’s a challenge worthy of seasoned astronomer with a large scope! Enjoy…

Friday, October 12 – Today in 1891, the Astronomical Society of France was established. Exactly one year later in 1892, astronomy great E. E. Barnard was hard at work using the new tool of photography and became the first to discover a comet – 1892 V – in this way!

Not only did Barnard use photography for comets, but his main interest of study was details within the Milky Way. Tonight let us take out binoculars or a telescope at the widest possible field of view and have a look at two such regions in the westering Aquila – The “Double Dark Nebula.”

Just northeast of Altair is bright star Gamma Aquilae, and about a fingerwidth west is a pair of Barnard discoveries: B142 and B143 – two glorious absences of stars known as interstellar dust clouds. B143 is no more than a half degree in size and will simply look like a blank area shaped like a horseshoe, with its extensions point toward the west. Just south is B142, an elongated comma shape, which seems to underline its companion.

Located anywhere from 1000 to 3000 light-years away, these non-luminous clouds of gas and dust are a very fine example of Barnard’s passion. Do not be upset if you don’t see them on your first attempt – for the chances are if you are seeing “nothing,” you are looking in the right place!

Saturday, October 13 – Today marks the founding of the British Interplanetary Society in 1933. “From imagination to reality,” the BIS is the world’s oldest established organization devoted solely to supporting and promoting the exploration of space and astronautics.

Tonight we’ll do them proud as we go back for another look at the mighty M2. You’ll find it located about three fingerwidths north-northeast of Beta Aquarii (RA 33.5 Dec 00 49).

At slightly dimmer than 6th magnitude, this outstanding globular cluster is just inside that region where it can’t quite be viewed unaided, but even the smallest of binoculars will pick it out of a relatively starless field with ease. Holding a Class II designation, it was first discovered by Maraldi on September 11, 1746 and rediscovered independently by Messier exactly 14 years later. At a distance of roughly 37,500 light-years, it is estimated to contain in the neighborhood of 150,000 stars.

Even a small telescope will reveal M2’s rich and concentrated core region and slight ellipticity. Not bad for a 13 billion year old group of stars! As aperture increases, some of the brightest stars will begin to resolve, and in larger telescopes it will approach total resolution. You might well note a dark area in the northeastern section, and several more located throughout the splendid field. Feast your eyes on one of the finest in the skies!

Sunday, October 14 – Before we leave Cygnus for the year, try your luck with IC 5070 (Right Ascension: 20 : 50.8 – Declination: +44 : 21), also known as the “Pelican Nebula.” You’ll find it just about a degree southeast of Deneb and surrounding the binary star 56 Cygni.

Located around 2000 light-years away, the Pelican is an extension of the elusive North American Nebula, NGC 7000. Given its great expanse and faintness, catching the Pelican does require clean skies, but it can be spotted best with large binoculars. As part of this huge star forming region, look for the obscuring dark dust cloud Lynds 935 to help you distinguish the nebula’s edges. Although it is every bit as close as the Orion Nebula, this star hatchery isn’t quite as easy!

Now let’s give deep sky a rest as we travel to the northwest corner of Capricornus and have a look just south of Alpha at beautiful Beta.

Named Dabih, this lovely white 3rd magnitude star has a very easily to split 6th magnitude companion which will appear slightly blue. Over 100 times brighter than our own Sun, the primary star is also a spectroscopic triple – one whose unseen companions orbit in a little over 8 days and 1374 days. Oddly enough the B star is also a very tight binary as well – yet the two major stars of this system are separated by about a trillion miles! If you have a large aperture telescope – power up. According to T. W. Webb, a 13th magnitude unrelated double is also found in between the two brighter stars. No matter if you chose binoculars or a telescope, I’m sure you’ll find the 150 light-year trip worth your time to add to your doubles list!

Until next week? Wishing you clear skies!

Posted on by Tammy Plotner

Weekly SkyWatcher’s Forecast: October 1-7, 2012

Greetings, fellow SkyWatchers! Normally we don’t pay much attention to the waning Moon, but this week will be a bit different. Why not enjoy some alternative studies by viewing familiar features in a different light?! Of course, we might just pick up a galaxy or catch a snowball! When you’re ready, just meet me in the back yard…

Monday, October 1 – In 1897, the world’s largest refractor (40?) debuted at the dedication of the University of Chicago’s Yerkes Observatory. The immense telescope was 64 feet long and weighed 6 tons. Also today in 1958, NASA was established by an act of Congress. More? In 1962, the 300 foot radio telescope of the National Radio Astronomy Observatory (NRAO) went live at Green Bank, West Virginia. It held its place as the world’s second largest radio scope until it collapsed in 1988. (It was rebuilt as a 100 meter dish in 2000.) Although first light for the 40? was Jupiter, E. E. Barnard later discovered the third companion star to Vega using the Yerkes refractor and first “light” studies at Green Bank were a radio source galaxy and pulsar for NRAO.

Tonight let’s begin our adventures by talking about Luna 9, also known as Lunik 9. In 1966, the unmanned Soviet lunar probe became the first to achieve a soft landing on the Moon’s surface and successfully transmit photographs back to Earth. The lander weighed in at 99 kg, and the four petals, which formed the spacecraft, opened outward. Within five minutes of landing, antennae sprang to life and the television cameras began broadcasting back the first panoramic images of the surface of another world, proving that a landing would not simply sink into the lunar dust. Last contact with the spacecraft occurred just before midnight on February 6, 1966.

Tonight you can view the area of the first successful landing on the Moon by turning your binoculars or telescopes copes towards the Oceanus Procellarum—the Ocean of Storms. While the area will be brightly lit and it will be difficult to pick out small features, Procellarum is the long, dark expanse that runs from lunar north to south. On its western edge, you can easily identify the dark oval of landmark crater Grimaldi. About one Grimaldi-length northward and on the western shore of Procellarum is where you would find the remains of Luna 9.

Tuesday, October 2 – Tonight before the skies get bright we’ll a have look at an incredible southern galaxy in Sculptor – NGC 253 (Right Ascension: 0 : 47.6 – Declination: -25 : 17).

Located about one third the way between Alpha Sculptor and Beta Ceti, NGC 253 was discovered by Caroline Herschel in 1783 during a comet search. As the brightest member of the “Sculptor Group”, this large and beautiful galaxy is also one of the closest outside our “Local Group” and will be readily apparent in binoculars for southern observers. Mid-to-large telescopes will be delighted with its many bright knots and dark obscured areas. For more northern observers, wait until the constellation is at its highest to catch a glimpse of this awesome 7th magnitude southern study.

Now, let’s wait for the Moon to rise!

For a telescope challenge, continue south to relocate previous study Petavius on the southern terminator. Just beyond its east wall, look for a bright ridge that extends from north to south separated by darkness from Petavius. This is Palitzsch, a very strange, gorge-like formation that looks as if it was caused by a meteor plowing through the Moon’s surface. Palitzsch’s true nature wasn’t known until 1954 when Patrick Moore resolved it as a “crater chain” using the 25″ Newall refractor at Cambridge University Observatory. While you’re admiring Petavius and its branching rima, keep in mind this 80 kilometer long crack is a buckle in the lava flow across the crater floor. Now look along the terminator for the long, dark runnel which is often considered to be the Petavius Wall but is actually the fascinating crater Palitzsch. This 41 kilometer wide crater is confluent with a 110 kilometer long valley that is outstanding at this phase!

Wednesday, October 3 – Tonight let’s go hunting for the “Blue Snowball”. It’s proper name is the NGC 7662 (Right Ascension: 23 : 25.9 – Declination: +42 : 33) and you find it around five degrees due east of Omicron Andromedae. At magnitude 9, this one challenges binocular users and presents the same problems as locating the M57 – low power will show you something – but not what it is. In a telescope, the “Blue Snowball” is almost as large as the “Ring” nebula.

Are you ready for the Moon to rise? Then let’s continue our waning studies…

As Mare Crisium slowly disappears into the shadows, let’s take a look for a lunar challenge crater – Macrobius. You’ll find it just northwest of the Crisium shore. Spanning 64 kilometers in diameter, this Class I impact crater drops to a depth of nearly 3600 meters – about the same as many of our earthly mines. Its central peak rises back up, and at 1100 meters may be visible as a small speck inside the crater’s interior. Power up and look at how steep its crater slopes are. Can you spot the smaller impact crater Macrobius O to the southeast and conjoining crater Tisserand to the east? Check out how the sunlight highlights the the west and southwest walls. In this particular light you can see how high and terraced they really are! Look for the impact of Macrobius C to the southwest.

In binoculars, look for the junction of Mare Fecunditatis and the edge of Mare Tranquillitatis. Here stands ancient Taruntius. Like a “lighthouse” guarding the shores, it stands on a mountainous peninsula overlooking the mare and shooting its brilliant beams across the desolate landscape nearly 175 kilometers.. Tonight it appears as a bright ring, but watch in the days ahead as it turns into just another crater.

Thursday, October 4 – Today in 1957, the USSR’s Sputnik 1 made space history as it became the first manmade object to orbit the earth. The Earth’s first artificial satellite was tiny, roughly the size of a basketball, and weighed no more than the average man. Every 98 minutes it swung around Earth in its elliptical orbit and changed everything. It was the beginning of the “Space Race.” Many of us old enough to remember Sputnik’s grand passes will also recall just how inspiring it was. Take the time with your children or grandchildren to check heavens-above.com for visible passes of the ISS and think about how much our world has changed in just 50 years!

Tonight we’re headed towards the southwest corner star of the Great Square of Pegasus – Alpha. Our goal will be 11th magnitude NGC 7479 located about 3 degrees south (RA 23:04.9 Dec +12:19).

Discovered by Sir William Herschel in 1784 and cataloged as H I.55, this barred spiral galaxy can be spotted in average telescopes and comes to beautiful life with larger aperture. Also known as Caldwell 44 on Sir Patrick Moore’s observing list, what makes this galaxy special is its delicate “S” shape. Smaller scopes will easily see the central bar structure of this 105 million light-year distant island universe, and as aperture increases, the western arm will become more dominant. This arm itself is a wonderful mystery – containing more mass than it should and a turbulent structure. It is believed that perhaps a minor merger may have at one time occurred, yet no evidence of a companion galaxy can be found.

On July 27, 1990, a supernova occurred near NGC 7479?s nucleus and reached a magnitude of 16. When observed in the radio band, there is a polarized jet near the bright nucleus that is unlike any other structure known. If at first you do not see a great deal of detail, relax… Allow your mind and eye time to look carefully. Even with telescopes as small as 8-10? structure can easily be seen. The central bar becomes “clumpy” and this well-studied Seyfert region is home to an abundance of molecular gas and forming stars.

Enjoy this incredible galaxy…

Friday, October 5 – Today marks the birthdate of Robert Goddard. Born 1882, Goddard is known as the father of modern rocketry – and with good reason.

In 1907, Goddard came into the public eye as a cloud of smoke erupted from the basement of the physics building in Worcester Polytechnic Institute where he had just fired a powder rocket. By 1914, he had patented the use of liquid rocket fuel and two- or three-stage solid fuel rockets. His work continued as he sought methods of putting equipment ever higher, and by 1920 he had envisioned his rockets reaching the Moon. Among his many achievements, he proved that a rocket would work in a vacuum, and by 1926 the first scientific equipment went along for the ride. By 1932, Goddard was guiding those flights and by 1937 had the motors pivoting on gimbals and controlled gyroscopically. His lifetime of work went pretty much unnoticed until the dawn of the Space Age, but in 1959 (14 years after his death) he received his acclaim at last as NASA’s Goddard Space Flight Center was established in his memory.

Today in 1923, Edwin Hubble was also busy as he discovered the first Cepheid variable in M31 – the Andromeda Galaxy. Hubble’s discovery was crucial in proving that objects once classed as “spiral nebulae” were actually independent and external stellar systems like our own Milky Way.

Tonight let’s look at a Cepheid variable as we head towards Eta Aquilae, almost a fistwidth due south of bright Altair.

Discovered by Edward Pigott in 1784, Eta is a Cepheid variable star around 1200 light-years away, but its beauty can be followed easily with the unaided eye. Ranging almost a full magnitude in a period of slightly over 7 days, this yellow supergiant is 3000 times brighter than our own Sun and around 60 times larger. Watch over the days as it takes about 48 hours to achieve maximum brightness and rivals nearby Beta – then falls slowly over the next 5 days.

If you’re still out when the Moon rises, look for a conjunction with the bright planet, Jupiter! For a handful of viewers in the south-western regions of Australia, this is the universal date of an occultation event, so be sure to check resources for websites like IOTA, which will give you précises times and locations for your area.

Saturday, October 6 – Have you been watching planetary motion? On this universal date, Mars leaves the constellation of Libra and enters Scorpius. For observers in the southern hemisphere, look for a conjunction of Mercury and Saturn at dusk. While time and the stars appear to stand still and astronomical twilight begins earlier each night, let’s take one last look at Antares. It’s a relatively old, massive star – very bright and destined to end brilliantly. Or Markab – an aging blue dwarf soon to become a red giant. Now look at Deneb. It’s a supermassive blue giant shining as brightly as some globular clusters – yet fated to create another supernova remnant in Cygnus within 100 thousand years… Take a look at Enif – a spectral class K orange supergiant radiating with as much light as 7000 suns – yet it burns fast and is cooler than Sol. How about Polaris? Hotter than Sol, it’s another star about to enter a glorious retirement. Thankfully, our Sun is right in the middle of the wonderful H-R diagram!

Now wait for the Moon to rise…

Tonight it is possible to see another landing area – that of Apollo 15. Locate previous northern study crater Plato and look due south past the isolated Spitzbergen Mountains to comparably-sized Archimedes. Spend a few moments enjoying Archimedes’ well-etched terraced walls and textured bright floor. Then look east look for the twin punctuations of Aristillus and the more northern Autolycus. South of Aristillus note the heart-shape of Paulus Putredinus. There you will see Mons Hadley very well highlighted and alone on its northeastern bank. Power up to see that the Mons Hadley area includes a cove known as the Hadley Delta, and there on that plain just north of the brilliant mountain peak is where Apollo 15 touched down. Enjoy it in sunset hues!

Your first challenge for the evening will be a telescopic one known as the Hadley Rille. Using our past knowledge of Mare Serenitatis, look for the break along its western shoreline that divides the Caucasus and Apennine mountain ranges. Just south of this break is the bright peak of Mons Hadley. You’ll find this area of highest interest for several reasons, so power up as much as possible.

Impressive Mons Hadley measures about 24 by 48 kilometers at its base and reaches up an incredible 4572 meters. If this mountain was indeed caused by volcanic activity on the lunar surface, this would make it comparable to some of the very highest volcanically caused peaks on Earth, such as Mount Shasta or Mount Rainer. To its south is the secondary peak Mons Hadley Delta—the home of the Apollo 15 landing site just a breath north of where it extends into the cove created by Palus Putredinus.

Along this ridgeline and smooth floor, look for a major fault line known as the Hadley Rille, winding its way across 120 kilometers of lunar surface. In places, the rille spans 1500 meters in width and drops to a depth of 300 meters below the surface. Believed to have been formed by volcanic activity some 3.3 billion years ago, we can see the impact that lower gravity has had on this type of formation, since earthly lava channels are less than 10 kilometers long and only around 100 meters wide. During the Apollo 15 mission, Hadley Rille was visited at a point where it was only 1.6 kilometers wide—still a considerable distance as seen in respect to astronaut James Irwin and the lunar rover. Over a period of time, its lava may have continued to flow through this area, yet it remains forever buried beneath years of regolith.

Sunday, October 7 – Today celebrates the birthday of Niels Bohr. Born 1885, Bohr was a pioneer Danish atomic physicist. Why not get up early – or stay up late – to enjoy more waning Moon studies?

Journey south of landmark Eratosthenes for an area known as Sinus Aestuum – the “Bay of Billows”. Its very smooth floor is curiously riddled to the north and east by dark stains. At one time Sinus Aestuum may have been completely submerged in basaltic lava across its 290 kilometer expanse. Later the molten rock sank to the Moon’s interior before it could do much more than melt away outer layers and older surface features. However, recent studies have shown mixing in the dark mantle terrain, as well as some areas which are spectrally different – dominated by what could be crystallized beads.

While at lower powers Sinus Aestuum seems to have very little to keep your interest, try magnifying and really take a look. Just to the southwest of Eratosthenes are the wonderful ruins of crater Stadius. This one is a real ghost! Stadius was form in the lower Imbrian period, so it’s not really that old, but the lava flow of Mare Insularum has pretty much taken it over. Very little remains that can be measured of its wall, but there are enough to throw some shadows to the northeast, and you can see the vague outline of companion crater Stadius A to the west. Look for all kinds of little craterlets dotting the floor; especially resolvable is Stadius K to the south and Stadius L, which appears lengthened to the southwest.

While you travel across the plains of Sinus Aestuum, look for the Rimae Bode and area which may be lighter because it contains a mixing of volcanic glasses and black beads. Crater Bode is nothing more than the tiny dark well along the eastern shore! The long rille in the center has no name, but if the shadows allow you to follow it south, you will end in several lava dome regions that belong to crater Gambart. This is just north of the Fra Mauro region and also home to the Surveyor 2 landing area! Just a bit more south will bring you to Fra Mauro and – as craters go – 3.9 billion year old Fra Mauro is on the shallow side and spans 95 kilometers. At some 730 meters deep, standing at the foot of one of its walls would be like standing at the bottom of the Grand Canyon… Yet, time has so eroded this crater that its west wall is completely missing and its floor is covered with fissures. Even though ruined Fra Mauro seems like a forbidding place to land a manned mission, it remained high on the priority list because it is geologically rich. Ill-fated Apollo 13 was to land in a formation north of the crater which was formed by ejecta belonging to the Imbrium Basin – material which had already been mapped telescopically. By returning samples of this material from deep within the Moon’s crust, scientists would have been able to determine the exact time these changes came about. As you view Fra Mauro tonight, picture yourself in a lunar rover traversing this barren landscape and viewing the rocks thrown out from a long-ago impact. How willing would you be to take on the vision of others and travel to another world?

Until next week? Ask for the Moon, but keep on reaching for the stars!

Lunar Image Courtesy of Mike Romine.

Posted on by Tammy Plotner

Weekly SkyWatcher’s Forecast: September 24-30, 2012

Plato Crater - Credit: Damian Peach

“Shine on, shine on Harvest Moon… Up in the sky…” Oh! Howdy, fellow SkyWatchers! The seasons are most surely showing their changes in both hemispheres and this week marks the famous “Harvest Moon”. The Moon will very much be in the eyepiece this week, so enjoy some great studies. However, don’t put away your telescopes just yet! Bright skies are a great time to catch up on double star studies and variables. Whenever you’re ready, just meet me in the back yard…

Monday, September 24 – In 1970, the first unmanned, automated return of lunar material to the Earth occurred on this day when the Soviet’s Luna 16 returned with three ounces of the Moon. Its landing site was eastern Mare Fecunditatis. Look just west of the bright patch of Langrenus. Let’s walk upon the Moon this evening as we take a look at sunrise over one of the most often studied and mysterious of all craters – Plato. Located on the northern edge of Mare Imbrium and spanning 95 kilometers in diameter, Class IV Plato is simply a feature that all lunar observers check because of the many reports of unusual happenings. Over the years, mists, flashes of light, areas of brightness and darkness, and the appearance of small craters have become a part of Plato’s lore.

On October 9, 1945 an observer sketched and reported “a minute, but brilliant flash of light” inside the western rim. Lunar Orbiter 4 photos later showed where a new impact may have occurred. While Plato’s interior craterlets average between less than one and up to slightly more than two kilometers in diameter, many times they can be observed – and sometimes they cannot be seen at all under almost identical lighting conditions. No matter how many times you observe this crater, it is ever changing and very worthy of your attention!

Although tonight’s bright skies will make our next target a little difficult to find visually, look around four fingerwidths southwest of Delta Capricorni (RA 21 26 40 Dec -22 24 40) for Zeta. Also known as 34 Capricorni, Zeta is a unique binary system. Located about 398 light-years from Earth, the primary star is a yellow supergiant with some very unusual properties – it’s the warmest, most luminous barium star known. But that’s not all, because the B component is a white dwarf almost identical in size to our own Sun!

Tuesday, September 25 – Tonight would be a great opportunity to take another look at crater Eratosthenes. Just slightly north of lunar center, this easily spotted feature dangles at the end of the Apennine Mountain range like a yo-yo caught on a string. Its rugged walls and central peaks make for excellent viewing. If you look closely at the mountains northeast of Eratosthenes, you will see the high peak of Mons Wolff. Named for the Dutch philosopher and mathematician, this outstanding feature reaches 35 kilometers in height. To the southwest of Era-tosthenes you may also spot the ruined remains of crater Stadius. Very little is left of its walls and the floor is dotted with small strikes. Near the twin pair of punctuations to its south lie the remains of Surveyor 2! Now let’s journey to a very pretty star field as we head toward the western wing tip in Cygnus to have a look at Theta – also known as 13 Cygni. It is a beautiful main sequence star that is also considered by modern catalogs to be a double. For large telescopes, look for a faint (13th magnitude) companion to the west… But it’s also a wonderful optical triple!

Also in the field with Theta to the southeast is the Mira-type variable R Cygni, which ranges in magnitude from around 7 to 14 in slightly less than 430 days. This pulsating red star has a really quite interesting history that can be found at AAVSO, and is circumpolar for far northern observers. Check it out!

Wednesday, September 26 – Tonight on the Moon, let’s take an in-depth look at one of the most impressive of the southern lunar features – Clavius.

Although you cannot help but be drawn visually to this crater, let’s start at the southern limb near the terminator and work our way up. Your first sighting will be the large and shallow dual rings of Casatus with its central crater and Klaproth adjoining it. Further north is Blancanus with its series of very small interior craters, but wait until you see Clavius. Caught on the southeast wall is Rutherford with its central peak and crater Porter on the northeast wall. Look between them for the deep depression labeled D. West of D you will also see three outstanding impacts: C, N and J; while CB resides between D and Porter. The southern and southwest walls are also home to many impacts, and look carefully at the floor for many, many more! It has been often used as a test of a telescope’s resolving power to see just how many more craters you can find inside tremendous old Clavius. Power up and enjoy!

And if you’d like to visit an object that only requires eyes, then look no further than Eta Aquilae one fist-width due south of Altair…

Discovered by Pigot in 1784, this Cepheid-class variable has a precision rate of change of over a magnitude in a period of 7.17644 days. During this time it will reach of maximum of magnitude 3.7 and decline slowly over 5 days to a minimum of 4.5… Yet it only takes two days to brighten again! This period of expansion and contraction makes Eta very unique. To help gauge these changes, compare Eta to Beta on Altair’s same southeast side. When Eta is at maximum, they will be about equal in brightness.

Thursday, September 27 – Tonight exploring the Moon will be in order as one of the most graceful and recognizable lunar features will be prominent – Gassendi. As an ancient mountain-walled plain that sits proudly at the northern edge of Mare Humorum, Gassendi sports a bright ring and a triple central mountain peak that are within the range of binoculars.

Telescopic viewers will appreciate Gassendi at high power in order to see how its southern border has been eroded by lava flow. Also of note are the many rilles and ridges that exist inside the crater and the presence of the younger Gassendi A on the north wall. While viewing the Mare Humorum area, keep in mind that we are looking at an area about the size of the state of Arkansas. It is believed that a planetoid collision originally formed Mare Humorum. The incredible impact crushed the surface layers of the Moon resulting in a concentric “anticline” that can be traced out to twice the size of the original impact area. The floor of this huge crater then filled in with lava, and was once thought to have a greenish appearance but in recent years has more accurately been described as reddish. That’s one mighty big crater!

Tonight we’ll begin with an easy double star and make our way towards a more difficult one. Beautiful, bright and colorful, Beta Cygni is an excellent example of an easily split double star. As the second brightest star in the constellation of Cygnus, Albireo lies roughly in the center of the “Summer Triangle” making it a relatively simple target for even urban telescopes.

Albireo’s primary (or brightest) star is around magnitude 4 and has a striking orangish color. Its secondary (or B) star is slightly fainter at a bit less than magnitude 5, and often appears to most as blue, almost violet. The pair’s wide separation of 34? makes Beta Cygni an easy split for all telescopes at modest power, and even for larger binoculars. At approximately 410 light-years away, this colorful pair shows a visual separation of about 4400 AU, or around 660 billion kilometers. As Burnham noted, “It is worth contemplating, in any case, the fact that at least 55 solar systems could be lined up, edge-to-edge, across the space that separates the components of this famous double!”

Now let’s have a look at Delta. Located around 270 light-years away, Delta is known to be a more difficult binary star. Its duplicity was discovered by F. Struve in 1830, and it is a very tough test for smaller optics. Located no more than 220 AU away from the magnitude 3 parent star, the companion orbits anywhere from 300 to 540 years and is often rated as dim as 8th magnitude. If skies aren’t steady enough to split it tonight, try again! Both Beta and Delta are on many challenge lists.

Friday, September 28 – Tonight our primary lunar study is crater Kepler. Look for it as a bright point, slightly lunar north of center near the terminator. Its home is the Oceanus Procellarum – a sprawling dark mare composed primarily of dark minerals of low reflectivity (albedo) such as iron and magnesium. Bright, young Kepler will display a wonderfully developed ray system. The crater rim is very bright, consisting mostly of a pale rock called anorthosite. The “lines” extending from Kepler are fragments that were splashed out and flung across the lunar surface when the impact occurred. The region is also home to features known as “domes” – seen between the crater and the Carpathian Mountains. So unique is Kepler’s geological formation that it became the first crater mapped by U.S. Geological Survey in 1962.

Up next, we’ll have a look at the central star of the “Northern Cross” – Gamma Cygni. Also known as Sadr, this beautiful main sequence star lies at the northern edge of the “Great Rift.” Surrounded by a field of nebulosity known as IC 1310, second magnitude Gamma is very slowly approaching us, but still maintains an average distance of about 750 light-years. It is here in the rich, starry fields that the great dust cloud begins its stretch toward southern Centaurus – dividing the Milky Way into two streams. The dark region extending north of Gamma towards Deneb is often referred to as the “Northern Coalsack,” but its true designation is Lynds 906.

If you take a very close look at Sadr, you will find it has a well-separated 10th magnitude companion star, which is probably not related – yet in 1876, S. W. Burnham found that it itself is a very close double. Just to its north is NGC 6910 (Right Ascension: 20 : 23.1 – Declination: +40 : 47), a roughly 6th magnitude open cluster which displays a nice concentration in a small telescope. To the west is Collinder 419, another bright gathering that is nicely concentrated. South is Dolidze 43, a widely spaced group with two brighter stars on its southern perimeter. East is Dolidze 10, which is far richer in stars of various magnitudes and contains at least three binary systems.

Whether you use binoculars or telescopes, chances are you won’t see much nebulosity in this region – but the sheer population of stars and objects in this area makes a visit with Sadr worthy of your time!

Saturday, September 29 – Tonight we’re going to have a look at a lunar feature that goes beyond simply incredible – it’s downright weird. Start your journey by identifying Kepler and head due west across Oceanus Procellarum until you encounter the bright ring of crater Reiner. Spanning 30 kilometers, this crater isn’t anything in particular – just shallow-looking walls with a little hummock in the center. But, look further west and a little more north for an anomaly – Reiner Gamma.

Well, it’s bright. It’s slightly eye-shaped. But what exactly is it? Possessing no real elevation or depth above the lunar surface, Reiner Gamma could very well be an extremely young feature caused by a comet. Only three other such features exist – two on the lunar far side and one on Mercury. They are high albedo surface deposits with magnetic properties. Unlike a lunar ray of material ejected from below the surface, Reiner Gamma can be spotted during the daylight hours – when ray systems disappear. And, unlike other lunar formations, it never casts a shadow.

Reiner Gamma also causes a magnetic deviation on a barren world that has no magnetic field. This has many proposed origins, such as solar storms, volcanic gaseous activity, or even seismic waves. But, one of the best explanations for its presence is a cometary strike. It is believed that a split-nucleus comet, or cometary fragments, once impacted the area and the swirl of gases from the high velocity debris may have somehow changed the regolith. On the other hand, ejecta from an impact could have formed around a magnetic “hot spot,” much like a magnet attracts iron filings. No matter which theory is correct, the simple act of viewing Reiner Gamma and realizing that it is different from all other features on the Moon’s earthward facing side makes this journey worth the time!

When you’re done, let’s head about a fingerwidth south of Gamma Cygni to have a look at an open cluster well suited for all optics – M29 (Right Ascension: 20 : 23.9 – Declination: +38 : 3).

Discovered in 1764 by Charles Messier, this type D cluster has an overall brightness of about magnitude 7, but isn’t exactly rich in stars. Hanging out anywhere from 6000 to 7200 light-years away, one would assume this to be a very rich cluster and it may very well have hundreds of stars – but their light is blocked by a dust cloud a thousand times more dense than average. Approaching us at around 28 kilometers per second, this loose grouping could be as old as 10 million years and appears much like a miniature of the constellation of Ursa Major at low powers. Even though it isn’t the most spectacular in star-rich Cygnus, it is another Messier object to add to your list!

Sunday, September 30 – Today in 1880, Henry Draper must have been up very early indeed when he took the first photo of the Great Orion Nebula (M42). Although you might not wish to set up equipment before dawn, you can still use a pair of binoculars to view this awesome nebula! You’ll find Orion high in the southeast for the Northern Hemisphere, and M42 in the center of the “sword” that hangs below its bright “belt” of three stars.

Our seasons are changing – and so the seasons change on other planets, too. Today marks the universal date on which Northern Autumn, Southern Spring Equinox occurs on Mars. Keep an eye for subtle changes in surface features of the red planet!

This is also the Universal date the Moon will become Full and it will be the closest to the Autumnal Equinox. Because its orbit is more nearly parallel to the eastern horizon, it will rise at dusk for the next several nights in a row. On the average, the Moon rises about 50 minutes later each night, but at this time of year it’s around 20 minutes later for mid-northern latitudes and even less farther north. Because of this added light, the name “Harvest Moon” came about because it allowed farmers more time to work in the fields.

Often times we perceive the Harvest Moon as being more orange than at any other time of the year. The reason is not only scientific enough – but true. Coloration is caused by the scattering of the light by particles in our atmosphere. When the Moon is low, like now, we get more of that scattering effect and it truly does appear more orange. The very act of harvesting itself produces more dust and often times that coloration will last the whole night through. And we all know the size is only an “illusion”…

So, instead of cursing the Moon for hiding the deep sky gems tonight, enjoy it for what it is…a wonderful natural phenomenon that doesn’t even require a telescope!

Until next week? Ask for the Moon, but keep on reaching for the stars!

Posted on by Tammy Plotner

Weekly SkyWatcher’s Forecast – September 17-23, 2012

Globular Cluster M15 from Hubble Space Telescope. There are likely one or more intermediate-mass black holes at its heart. Courtesy: ESA, Hubble, NASA
Globular Cluster M15 from Hubble Space Telescope. There are likely one or more intermediate-mass black holes at its heart. Courtesy: ESA, Hubble, NASA

Greetings, fellow SkyWatchers! This looks like a great week to take in some galactic star clusters and enjoy the Andromeda Galaxy! Some lucky viewers are in for a Mars occultation event and everyone wins with a meteor shower. What’s that, you say? Darn right. This week is also the time of the Autumnal Equinox! When ever you’re ready to learn more, just meet me in the back yard…

Monday, September 17 – Today in 1789, William Herschel discovered Saturn’s moon Mimas.

Tonight we’ll hunt with the “Fox” as we head to Vulpecula to try two more open star cluster studies. The first can be done easily with large binoculars or a low power scope. It’s a rich beauty that lies in the constellation of Vulpecula, but is more easily found by moving around 3 degrees southeast of Beta Cygni.

Known as Stock 1, this stellar swarm contains around 50 or so members of varying magnitudes that you will return to often. With a visual magnitude of near 5, loose associations of stars – like Stock clusters – are the subject of recent research. The latest information indicates that the members of this cluster are truly associated with one another.

A little more than a degree to the northeast is NGC 6815 (Right Ascension:19 : 40.9 – Declination: +26 : 51). While this slightly more compressed open cluster has no real status amongst deep sky objects, it is another one to add to your collection of things to do and see!

Tuesday, September 18 – Tonight we’ll start with an asterism known as the “Coat Hanger,” but it is also known as Brocchi’s Cluster, or Collinder 399. Let the colorful double star Beta Cygni – Albireo – be your guide as you move about 4 degrees to its south-southwest. You will know this cluster when you see it, because it really does look like a coat hanger! Enjoy its red stars.

First discovered by Al Sufi in 964 AD, this 3.5 magnitude collection of stars was again recorded by Hodierna. Thanks to its expansive size of more than 60 arc minutes, it escaped the catalogues of both Messier and Herschel. Only around a half dozen stars share the same proper motion, which may make it a cluster much like the Pleiades, but studies suggest it is merely an asterism…but one with two binary stars at its heart.
And for larger scopes? Fade east to the last prominent star in the cluster and power up. NGC 6802 (Right Ascension: 19 : 30.6 – Declination: +20 : 16) awaits you! At near magnitude 9, Herschel VI.14 is a well compressed open cluster of faint members. The subject of ongoing research in stellar evolution, this 100,000 year old cluster is on many observing challenge lists!

Wednesday, September 19 – On this day in 1848, William Boyd was watching Saturn – and discovered its moon Hyperion. On this date a moon will be on everyone’s mind as our Moon occults Mars (Pacific, South America, SW Atlantic). Be sure to check information such as the International Occultation Timing Assoication (IOTA) for specific details in your area. Even if you aren’t in a position to catch the occultation, it will still make a splendid scene! Also today in 1988, Israel launched its first satellite. How long has it been since you’ve watched an ISS pass or an iridium flare? Both are terrific events that don’t require any special equipment to be seen. Be sure to check with Heavens Above for accurate times and passes in your location and enjoy!

Tonight we again visit the M15 (Right Ascension: 21 : 30.0 – Declination: +12 : 10) globular and learn more about the scale of the Universe – circa 1900. On a decent night, a modest telescope will resolve about a dozen 13th magnitude stars outside M15?s core region. Most of these stars are red giants with absolute magnitudes of -2. Such stars appear 15 magnitudes fainter than they would be if they were at an astronomically standardized distance. Based on this 15 magnitude loss in intensity, we should be able to figure out how far away M15 is, but this is circular reasoning. In the early 1900s, astronomers didn’t know that the brightest stars in M15 were absolute magnitude -2. They first needed to know how far away the globular was to make sense of that.

Here’s where the H-R diagram helps out.

The most massive and swollen red giants (those nearing the end of their lives such as Betelgeuse and Antares) can be as luminous as absolute magnitude -6, but you can’t assume that the brightest red giants in a globular cluster are as bright as Antares and Betelgeuse. Why? Because we later discovered that all stars in a globular cluster entered the main sequence about the same time – some 12 billion years ago. Meanwhile, the very brightest ones – the Denebs – are no longer around. They exited the main sequence, became red giants and exploded a long, time ago, and possibly in a dwarf galaxy far, far away!

Now let’s take a a stellar tour of Lyra! First we’ll look at a double which has a close separation – Epsilon Lyrae. Known to most of us as the “Double Double,” look about a finger width northeast of Vega. Even the slightest optical aid will reveal this tiny star as a pair, but the real treat is with a telescope – for each component is a double star! Both sets of stars appear as primarily white and both are very close to each other in magnitude. What is the lowest power that you can use to split them?

Now let’s head for the northeast corner of the little parallelogram that is part of Lyra for easy unaided eye and binocular double Delta 1 and 2 Lyrae.

The westernmost Delta 1 is about 1100 light-years away and is a class B dwarf, but take a closer look at brighter Delta 2. This M-class giant is only 900 light-years away. Perhaps 75 million years ago, it, too, was a B class star, but it now has a dead helium core and it keeps on growing. While it is now a slight variable, it may in the future become a Mira-type. A closer look will show that it also has a true binary system nearby – a tightly matched 11th magnitude system. Oddly enough they are the same distance away as Delta-2 and are believed to be physically related.

Thursday, September 20 – Now let the Moon head west, because on this night in 1948, the 48? Schmidt telescope at Mt. Palomar was busy taking pictures. The first photographic plate was being exposed on a galaxy by the same man who ground and polished the corrector plate for this scope – Hendricks. His object of choice was reproduced as panel 18 in the Hubble Atlas of Galaxies and tonight we’ll join his vision as we take a look at the fantastic M31 – the Andromeda Galaxy.

Seasoned amateur astronomers can literally point to the sky and show you the location of M31 (Right Ascension: 0 : 42.7 – Declination: +41 : 16), but perhaps you have never tried. Believe it or not, this is an easy galaxy to spot even under the moonlight. Simply identify the large diamond-shaped pattern of stars that is the “Great Square of Pegasus.” The northernmost star is Alpha, and it is here we will begin our hop. Stay with the north chain of stars and look four finger-widths away for an easily seen star. The next along the chain is about three finger-widths away… And we’re almost there. Two more finger-widths to the north and you will see a dimmer star that looks like it has something smudgy nearby. Point your binoculars there, because that’s no cloud – it’s the Andromeda Galaxy!

Friday, September 21 – And what was Sir William Herschel doing on this date a couple of centuries ago? You can bet he was out telescoping; and his discoveries on this night were many. How about if we take a look at two logged on September 21 which made the Herschel “400? list?

Our first stop is northern Cygnus for NGC 7086 (RA 21 30 30 Dec +51 35 00). Located on the galactic equator about five degrees west of Beta Cephei, our target is an open cluster. At magnitude 8.4, this loose collection will be difficult for the smaller scope, and show as not much more than an arrow-like asterism. However, larger scopes will be able to resolve many more stars, arrayed in long loops and chains around the brighter members. Although it’s sparse, NGC 7086 has been studied for metal abundance, galactic distance, membership richness, and its luminosity function. Be sure to mark your notes for H VI.32, logged by Herschel in 1788.

Now hop on over to Andromeda for NGC 752 (RA 01 57 41 Dec +37 47 06). You’ll find it just a few degrees south of Gamma and in the field north of star 56. Located 1300 light-years away, there’s a strong possibility this cluster was noted first by Hodierna before being cataloged by Herschel on this night (1786). At near magnitude 5, this “400? object is both large and bright enough to be seen in binoculars or small telescopes, and people have often wondered why Messier did not discover it. The star-studded field containing about 70 members of various magnitudes belong to H VII.32 – a very old cluster which has more recently been studied for its metallicity and the variations in the magnetic fields of its members. Enjoy them both tonight! Sir William did…

Saturday, September 22 – Today marks the universal date of Autumnal Equinox. Enjoy this “equal” period of day and night!

Tonight we’ll return again to Vulpecula – but with a different goal in mind. What we’re after requires dark skies – but can be seen in both binoculars and a small telescope. Once you’ve found Alpha, begin about two fingerwidths southeast and right on the galactic equator you’ll find NGC 6823 (Right Ascension: 19 : 43.1 – Declination: +23 : 18).

The first thing you will note is a fairly large, somewhat concentrated magnitude 7 open cluster. Resolved in larger telescopes, the viewer may note these stars are the hot, blue/white variety. For good reason. NGC 6823 only formed about 2 billion years ago. Although it is some 6000 light-years away and occupies around 50 light-years of space, it’s sharing the field with something more – a very large emission/reflection nebula, NGC 6820 (Right Ascension: 19 : 43.1 – Declination: +23 : 17).

In the outer reaches of the star cluster, new stars are being formed in masses of gas and dust as hot radiation is shed from the brightest of the stellar members of this pair. Fueled by emission, NGC 6820 isn’t always an easy visual object – it is faint and covers almost four times as much area as the cluster. But trace the edges very carefully, since the borders are much more illuminated than the region of the central cluster. Take the time to really observe this one! Its processes are very much like those of the “Trapezium” area in the Orion nebula. Be sure to mark your observing notes. NGC 6823 is Herschel VII.18 and NGC 6820 is also known as Marth 401!

Now we’re off to a spectacular open cluster – NGC 6940. At close to magnitude 6, you’ll find this unsung symphony of stars around three fingerwidths southwest of Epsilon Cygni (RA 20 34 24.00 Dec +28 17 -0.0).

Discovered by Sir William Herschel on Oct 15, 1784, and logged as H VIII.23, this intermediate aged galactic cluster will blow your mind in larger aperture. Visible in binoculars, as size increases the field explodes into about 100 stars in a highly compressed, rich cloud. Although it is not an often visited cluster, it is part of many observing challenge lists. Use low power to get the full effect of this stunning starfield!

Sunday, September 23 – On this day in 1846, Johann Galle of the Berlin Observatory makes a visual discovery. While at the telescope, Galle sees and identifies the planet Neptune for the first time in history. On this day in 1962, the prime time cartoon “The Jetsons” premiered. Think of all the technology this inspired!

Rather than doing lunar work tonight, why not wait until the Moon has westered and have an “Autumn Planetary Marathon”? Start easy with M57 between Gamma and Beta Lyrae. Head north-northwest to the “Cat’s Eye” (NGC 6543) roughly between Delta and Zeta Draconis – you’ll need your charts for this one! Now southwest to the “Blinking Planetary” (NGC 6543) – found less than three degrees east-southeast of Iota Cygni. Continue east-southeast a little less than 6 degrees past Deneb to the “Box Planetary” – NGC 7027. Now on to the brightest of the ten – M27. The “Dumbbell Nebula” is located a little more than 3 degrees north of Gamma Sagittae. Now drop two hand spans south to the “Little Gem” (NGC 6818) – around 7 degrees northeast of Rho Sagittarii.

One hand span east of the “Little Gem” leads you toward the “Saturn Nebula” in Aquarius – a little more than a degree west of Nu. Now it’s a huge jump of more than two hand spans west-northwest to tiny NGC 6572 – located around two finger-widths south-southeast of 72 Ophiuchi. Continue on to compact NGC 6790 a finger-width south of Delta Aquilae. Did you find them all? Well, if the “Cat’s Eye” is the toughest to locate, then NGC 6790 is the hardest to identify. Good going! But don’t stop now… Two hand spans west-northwest leads to NGC 6210 – best located using pointer stars Gamma and Beta Herculis. Excellent work!

Ready for the finale? Now, kick back… relax… and watch the Alpha Aurigid meteor shower. Face northeast and look for the radiant near Capella. The fall rate is around 12 per hour, and they are fast and leave trails!

Until next week? Wishing you clear skies…

Posted on by Tammy Plotner

Weekly SkyWatcher’s Forecast: September 10-16, 2012

Greetings, fellow SkyWatchers! With very little Moon to contend with this week, it will be a great time to take on some challenging studies like the Helix Nebula, Saturn Nebula, Stephen’s Quintet and more. It’s time to get out your big telescope and head for some dark skies… Because this week isn’t for the beginner! Whenever you’re ready, I’ll see you out back…

Monday, September 10 – Today is the birthday of James E. Keeler. Born in 1857, the American Keeler was a pioneer in the field of spectroscopy and astrophysics. In 1895, Keeler proved that different areas in Saturn’s rings rotate at different velocities. This clearly showed that Saturn’s rings were not solid, but were instead a collection of smaller particles in independent orbits.

Now, let’s head on to Capricornus and drop about four finger-widths south of its northeastern most star – Delta – and have a look at M30 (Right Ascension: 21 : 40.4 – Declination: -23 : 11). Discovered in 1764 by Charles Messier, binocular observers will spot this small, but attractive, globular cluster easily in the same field with star 41. For telescopic observers, you will find a dense core region and many chains of resolvable stars in this 40,000 light year distant object. Power up!

Let’s get some more practice in Capricornus, and take on a more challenging target with confidence. Locate the centermost bright star in the northern half of the constellation – Theta – because we’re headed for the “Saturn Nebula”.

Three finger-widths north of Theta you will see dimmer Nu, and only one finger-width west is NGC 7009 (Right Ascension: 21 : 04.2 – Declination: -11 : 22). Nicknamed the “Saturn Nebula”, this wonderful blue planetary is around 8th magnitude and achievable in small scopes and large binoculars. Even at moderate magnification, you will see the elliptical shape which gave rise to its moniker. With larger scopes, those “ring like” projections become even clearer, making this challenging object well worth the hunt. You can do it!

Tuesday, September 11 –Today celebrates the birthday of Sir James Jeans. Born in 1877, English-born Jeans was an astronomical theoretician. During the beginning of the 20th century, Jeans worked out the fundamentals of the process of gravitational collapse. This was an important contribution to the understanding of the formation of solar systems, stars, and galaxies.

So, are we ready to try for the “Helix”?

Located in a sparsely populated area of the sky, this intriguing target is about a fist width due northwest of bright Formalhaut and about a fingerwidth west of Upsilon Aquarii. While the NGC 7293 (Right Ascension: 22 : 29.6 – Declination: -20 : 48) is also a planetary nebula, its entirely different than most… It’s a very large and more faded edition of the M57! On a clear, dark night it can be spotted with binoculars since it spans almost one quarter a degree of sky. Using a telescope, stay at lowest power and widest field, because it is so large. It you have an OIII filter, this faded “ring” becomes a braided treat!

Wednesday, September 12 – Today in 1959, the USSR’s Luna 2 scored a mark as it became the first manmade object to hit the moon. The successful mission landed in the Paulus Putredinus area. Today also celebrates the 1966 Gemini 11 launch.

Tonight let’s take the time to hunt down an often overlooked globular cluster – M56. Located roughly midway between Beta Cygni and Gamma Lyrae (RA 19 15 35.50 Dec +30 11 04.2), this class X globular was discovered by Charles Messier in 1779 on the same night he discovered a comet, and was later resolved by Herschel. At magnitude 8 and small in size, it’s a tough call for a beginner with binoculars, but is a very fine telescopic object. With a general distance of 33,000 light-years, this globular resolves well with larger scopes, but doesn’t show as much more than a faint, round area with small aperture. However, the beauty of the chains of stars in the field makes it quite worth the visit!

While you’re there, look carefully: M56 is one of the very few objects for which the photometry of its variable stars was studied strictly with amateur telescopes. While one bright variable star had been known previously to exist, up to a dozen more have recently been discovered. Of those, six had their variability periods determined using CCD photography and telescopes just like yours!

Thursday, September 13 – Today in 1922, the highest air temperature ever recorded at the surface of the Earth occurred. The measurement was taken in Libya and burned in at a blistering 136F (58C), but did you know that the temperatures in the sunlight on the Moon double that? If you thought the surface of the Moon was a bit too warm for comfort, then know surface temperatures on the closest planet to the Sun can reach up to 800F (427C) at the equator during the day! As odd as it may sound, even that close to the Sun – Mercury could very well have ice deposits hidden below the surface at its poles.

Tonight we’ll move on to Aquila and look at the hot central star of an interesting planetary nebula – NGC 6804 (Right Ascension: 19 : 31.6 – Declination: +09 : 13). You’ll find it almost 4 degrees due west of Altair. Discovered by Herschel and classed as open cluster H VI.38, it wasn’t until Pease took a closer look that its planetary nature was discovered. Interacting with clouds of interstellar dust and gases, NGC 6804 is a planetary in decline, with its outer shell around magnitude 12 and the central star at about magnitude 13. While only larger telescopes will get a glimpse of the central, it’s one of the hottest objects in space – with temperatures around 30,000K!

If that’s not “hot” enough for you, then take a look straight overhead at brilliant star Vega. It is a “Sirian type” star and with a surface temperature of about 9200 degrees Kelvin, it’s twice as hot as our own Sun. At around 27 light years away, our entire solar system is moving towards Vega at a speed of 12 miles per second, but don’t worry… It will take us another 450,000 years to get there. If we were to arrive tonight, we’d find that Vega is around 3 times larger than Sol and that it also has a 10th magnitude companion that can often be resolved in mid-sized scopes. It’s one of the first stars to ever be photographed. Back in 1850, that simple star – Vega – took and exposure time of 100 seconds through a 15? scope. How times have changed!

Friday, September 14 – Tonight’s destination is not an easy one, but if you have a 6? or larger scope, you’ll fall in love a first sight! Let’s head for Eta Pegasi and slightly more than 4 degrees north/northeast for NGC 7331 (Right Ascension: 22 : 37.1 – Declination: +34 : 25).

This beautiful, 10th magnitude, tilted spiral galaxy is very much how our own Milky Way would appear if we could travel 50 million light years away and look back. Very similar in both structure to ourselves and the “Great Andromeda”, this particular galaxy gains more and more interest as scope size increases – yet it can be spotted with larger binoculars. At around 8? in aperture, a bright core appears and the beginnings of wispy arms. In the 10? to 12? range, spiral patterns begin to emerge and with good seeing conditions, you can see “patchiness” in structure as nebulous areas are revealed and the western half is deeply outlined with a dark dustlane. But hang on… Because the best is yet to come!

Saturday, September 15 – In 1991 the Upper Atmosphere Research Satellite (UARS) was launched from Space Shuttle Discovery. The successful mission lasted well beyond its life expectancy – sending back critical information about our ever-changing environment. After 14 years and 78,000 orbits, UARS remains a scientific triumph.

If you’re up early, why not check out Mars? While the red planet is visible, it’s also rather small at the moment, with an apparent diameter of less than .5”. Can you still spot some surface details?

Tonight return to the NGC 7331 with all the aperture you have. What we are about to look at is truly a challenge and requires dark skies, optimal position and excellent conditions. Now breathe the scope about one half a degree south/southwest and behold one of the most famous galaxy clusters in the night.
In 1877, French astronomer – Edouard Stephan was using the first telescope designed with a reflection coated mirror when he discovered something a bit more with the NGC 7331. He found a group of nearby galaxies! This faint gathering of five is better known as “Stephan’s Quintet” and its members are no further apart than our own Milky Way galaxy.

Visually in a large scope, these members are all rather faint, but their proximity is what makes them such a curiosity. The Quintet is made up of five galaxies numbered NGC 7317, 7318, 7318A, 7318B, 7319 and the largest is 7320 (Right Ascension: 22 : 36.1 – Declination: +33 : 57). Even with a 12.5? telescope, this author has never seen them as much more than tiny, barely there objects that look like ghosts of rice grains on a dinner plate. So why bother?

What our backyard equipment can never reveal is what else exists within this area – more than 100 star clusters and several dwarf galaxies. Some 100 million years ago, the galaxies collided and left long streamers of their materials which created star forming regions of their own, and this tidal pull keeps them connected. The stars within the galaxies themselves are nearly a billion years old, but between them lay much younger ones. Although we cannot see them, you can make out the soft sheen of the galactic nucleii of our interacting group.

Enjoy their faint mystery!

Sunday, September 16 – It’s New Moon! For those of you who have waited on the weekend to enjoy dark skies, then let’s add another awesome galaxy to the collection. Tonight set your sights towards Alpha Pegasi and drop due south less than 5 degrees to pick up NGC 7479 (Right Ascension: 23 : 04.9 – Declination: +12 : 19).

Discovered by William Herschel in 1784. this tantalizing 11 magnitude barred spiral galaxy has had a supernova in its nucleus as recently as 1990. While the 16th magnitude event is no longer visible, smaller telescopes will easily pick out bright core and elongation of the central bar. Larger aperture will find this one a real treat as the spiral arms curl both over and under the central structure, resembling a ballet dancer “en pointe”. Congratulations! You’ve just observed Caldwell 44.

Until next week? Wishing you clear skies!

Written by Tammy Plotner. NGC 7009 Image Credit: NOAO/AURA/NSF

Posted on by Tammy Plotner

Weekly SkyWatcher’s Forecast: August 27-September 2, 2012

Greetings, fellow SkyWatchers! If you only get your telescope or binoculars out once in a Blue Moon, then get them out this week when a Blue Moon actually happens! However, if you can’t wait, then let’s explore some great lunar features, bright star clusters and great double stars. When you’re ready to learn some history, mystery and more, then just step on inside…

Monday, August 27 – Tonight the waxing Moon’s most notable features will be the vast area of craters dominating the south-central portion near and along the terminator. Now emerging is Ptolemaeus – just north-northeast of Albategnius. This large round crater is a mountain walled plain filled with lava flow. With the exception of interior crater Ptolemaeus A, binoculars will see it as very smooth. Telescopes, however, can reveal faint mottling in the surface of the crater’s interior, along with a single elongated craterlet to the northeast. Despite its apparent uniformity, close inspection has revealed as many as 195 interior craterlets within Ptolemaeus! Look for a variety of interior ridges and shallow depressions.

With the Moon low to the southwest, we have a chance to go northeast to Cepheus for a new study – NGC 7160 (Right Ascension: 21 : 53.7 (hours : minutes) Declination: +62 : 36). At magnitude 6.1, this small open cluster is easily identified in scopes and may be seen as a faint starfield in binoculars. You’ll find it about a finger-width north of Nu Cephei.

Tuesday, August 28 – In 1789 on this day, Sir William Herschel discovered Saturn’s moon Enceladus.

On the lunar surface tonight, we’ll start by following the southward descent of large crater rings Ptolemaeus, Alphonsus, and Arzachel to a smaller, bright one southwest named Thebit. We’re going to have a look at Hell…

Just west of Thebit and its prominent A crater to the northwest, you see the Straight Wall – Rupes Recta – appearing as a thin, white line. Continue south until you see large, eroded crater Deslandres. On its western shore, is a bright ring that marks the boundary of Hell. While this might seem like an unusual name for a crater, it was named for an astronomer – and clergyman!

Once you’ve been to Hell, let’s go to the heavens for NGC 7235 (Right Ascension: 22 : 12.6 – Declination: +57 : 17). Locate the star crowded area of Epsilon Cephei which will also include this 7.7 magnitude open cluster in the same low power field. Give it a try. Look for a small, rectangular assortment of 10th magnitude and fainter stars, including a beautiful ruby red, west-northwest of Epsilon.

Wednesday, August 29 – Due south of mighty Copernicus on the eastern edge of Mare Cognitum, you will see a ruined pair of flattened craters. They are Bonpland and Parry – with Frau Mauro just above them. The smallest and brightest of these ancient twins is the eastern Parry. Have a look at its south wall where a huge section is entirely lost. It was near this location that Ranger 7 ended its successful flight in 1964. Just south of Parry is another example of a well-worn Class V crater. See if you can distinguish the ruins of Guericke. Not much is left save for a slight U-shape to its battered walls. These are some of the oldest visible features on the Moon!

If you’d like to head for something very young, have a look at 6.8 magnitude open cluster NGC 6811 (Right Ascension: 19 : 37.3 – Declination: +46 : 23) in Cygnus. This mid-sized, unusually dense open cluster is found less than finger-width north-northwest of Delta – the westernmost star of the Northern Cross. Like most open clusters, the age of NGC 6811 is measured in millions, rather than billions, of years. Visible in binoculars on most nights, telescopes should show a half dozen or so broadly-spaced resolvable stars overlaying a fainter field. Be sure to return again on a moonless night, and have another look a disparate double Delta!

Thursday, August 30 – Today celebrates the Yohkoh Mission, launched in 1991. It was a joint effort of both Japan and the United States to monitor solar flares and the corona. While its initial mission was quite successful, on December 14, 2001 the signal was lost during a total eclipse. Unable to reposition the satellite back towards the Sun, the batteries discharged and Yohkoh became inoperable.

While the graceful Gassendi will try to steal the lunar show tonight, let’s have a go at Foucault instead. To find it, head north to Sinus Iridum and locate Bianchini in the Juras Mountains. Just northeast, and near the shore of south-eastern Mare Frigoris, look for a bright little ring.

Physicist Jean Foucault played an instrumental role in the creation of today’s parabolic mirrors. His “Foucault knife edge test” made it possible for opticians to test mirror curves for optical excellence during the final phases of shaping before metallization. Thanks to Foucault’s insight, we can turn our telescopes on such difficult double stars as Beta Delphini and resolve its 0.6 arc-second distant 5.0 magnitude companion. A challenge for smaller scopes is MU Cygni. This 4.5 and 6.0 magnitude pair should be resolvable in any scope that passed Foucault’s test!

Tonight let’s view a double star, Eta Lyra. Just on the edge of unaided visibility, you will find it around three finger-widths due east of Vega. This wide, disparate pair of 4.5 and 8.0 magnitude stars should be resolvable in just about any scope, but is beyond the reach of binoculars.

Friday, August 31 – Tonight we will begin entering the stream of the Andromedid meteor shower, which peaks off and on for the next couple of months. For those of you in the northern hemisphere, look for the lazy “W” of Cassiopeia to the northeast. This is the radiant – or relative point of origin – for this meteor stream. At times, this shower has been known to be spectacular, but let’s stick with an accepted fall rate of around 20 per hour. These are the offspring of Beila’s Comet, one that split apart leaving radically different streams – much like 73/P Schwassman-Wachmann did last year. These meteors have a reputation for red fireballs with spectacular trains, so watch for them in the weeks ahead.

It’s Blue Moon! That doesn’t mean the Moon is going to be colored any differently – it just means it’s the second full Moon within a month.

Think having all this Moon around is the pits? Then let’s venture to Zeta Sagittarii and have a look at Ascella – “The Armpit of the Centaur.” While you’ll find Zeta easily as the southern star in the handle of the teapot formation, what you won’t find is an easy double. With almost identical magnitudes, Ascella is one of the most difficult of all binaries. Discovered by W. C. Winlock in 1867, the components of this pair orbit each other very quickly – in just a little more than 21 years. While they are about 140 light-years away, this gravitationally bound pair waltz no further apart than our own Sun and Uranus!

Too difficult? Then have a look at Nu Sagittarii – Ain al Rami, or the “Eye of the Archer.” It’s one of the earliest known double stars and was recorded by Ptolemy. While Nu 1 and Nu 2 are actually not physically related to one another, they are an easy split in binoculars. Eastern Nu 2 is a K type spectral giant that is around 270 light-years from our solar system. But take a very close look at the western Nu 1 – while it appears almost as bright, this one is 1850 light-years away! As a bonus, power up in the telescope, because this is one very tight triple star system!

Saturday, September 1 – On this day 1859, solar physicist Richard Carrington (who originally assigned sunspot rotation numbers) observed the first solar flare ever recorded. Naturally enough, an intense aurora followed the next day. 120 years later in 1979, Pioneer 11 made history as it flew by Saturn.

While the Moon essentially appears to be full throughout the night, take the time to compare the western and eastern limbs. To the west, you will see the smooth arc no longer displays high contrast features. To the east you should see a broken edge now in sunset. Watch in the days ahead as many of your favorite craters begin to reveal themselves in a “different light.”

Tonight let’s visit Alya. One of the fainter stars to receive a proper name, Theta Serpens Caput is located around a hand span due east of Beta Ophiuchi. Thankfully, resolving this wide, matched magnitude pair is easier than finding it. If you have high power, self-stabilizing binoculars, this one could be real fun!

Sunday, September 2 – It won’t be long until the Moon lights the skies, so let’s have a look at disparate double Kappa Pegasi. It’s the westernmost star of northern Pegasus and is around a hand span due south of Sadr – the central star of the Northern Cross. At magnitude 4.3, look for a faint companion leading the orange-yellow primary across the sky. This one could be tough for small scopes – so make a challenge of it!

Now let’s have a look at Beta and Gamma Lyrae – the lower two stars in the “Harp.” Beta is actually a quick change variable dropping to less than half the brightness of Gamma every 12 days, but for a few days the two stars appear to be of near equal brightness. Beta is a very unusual eclipsing spectroscopic binary. Its unseen companion may be a “collapsar.”
Before you call it a night, head a finger-width north of Omicron Andromedae for 15 Lacertae. Just on the edge of unaided visibility, this carbon star is also a disparate double. The 5.2 magnitude variable primary will appear more red at its faintest, but its 11.0 magnitude companion is the faintest of all!

But don’t put the telescope away just yet. If you can locate the Moon, you can locate Uranus! Just take a look about 3 degrees away to lunar south to catch the slightly greenish orb of the outer planet.

Until next week, ask for the Moon… But keep on reaching for the stars!

Ptolemaeus Crater Image Credit: Damian Peach

Posted on by Tammy Plotner

Weekly SkyWatcher’s Forecast: August 20-26, 2012

Crater Petavius - Credit: Damian Peach

Greetings, fellow SkyWatchers! It’s going to be a great week to catch up on your lunar studies, but be sure to mark your calendar for Tuesday’s splendid conjunction! There will be bright stars and clusters to study, so enjoy these temperate nights while they last! Whenever you’re ready to learn more about the history, mystery and majesty of what’s out there, meet me in the back yard…

Monday, August 20 – Tonight the Moon sets by skydark, but if you’re looking for a lunar challenge, return to crater Petavius about one-third the way up from the southern cusp just after sunset. This ancient crater is a wonderland of detail when lying on the terminator. Look for its rugged walls interrupted by crater Wrottesley to the northwest and elongated Palitzsch southeast. If conditions are stable, power up to look for a massive, multi-peaked central mountain region, along with a deep scar – Rima Petavius – cutting diagonally across the wavelike floor.

When the Moon has set, look for the southern Crown – Corona Australis. Its hidden jewel is 7.3 magnitude, 28,000 light-year distant globular cluster NGC 6723 (Right Ascension: 18 : 59.6 – Declination: -36 : 38). Discovered on June 3, 1826 by James Dunlop of New South Wales, Australia, NGC 6723 can be best found by heading less than 7 degrees due south of Zeta Sagittarii. This mid-sized cluster gives a surprising view, but if you’re more north, best catch it at its highest.

Now, relax! Tonight is the peak of the Kappa Cygnid meteor shower. Although the Moon will interfere early in the evening, wait until it has set and watch the area near Deneb. Discovered in the late 1800?s, the Kappa Cygnids are often overlooked because the grander, more prolific Perseids tend to get more attention. Although the stream has been verified, peak dates and fall rates vary from year to year. The average fall rate is usually no more than 5 per hour, but it is not uncommon to see 12 or more per hour with many fireballs. The stream’s duration is around 15 days. Clear skies!

Tuesday, August 21 – Deep Blue Celestial Scenery Alert! Don’t goof around tonight. Find yourself an open western horizon and be outside at sky dark for the awe inspiring combination of the Moon, Spica, Mars and Saturn. The powerful blue/white star will be located just northeast of the lunar edge while Mars resides to the east/southeast and Saturn reigns above them all. This will be a very photographic opportunity, so be sure to take advantage of this splendid conjunction. Tell your family and friends!

Although we have traveled this road before, let’s go further south than last night’s lunar study and have another look at Furnerius. Shallower and less impressive than Petavius, Furnerius will fade to obscurity as the Moon waxes. This flooded old crater has no central peak, but a much younger crater has punched a hole in its lava-filled floor. Look for the long “crack” extending from Furnerius’ north shore to crater rim. Perhaps it was caused by the impact? Sharp-eyed observers with good conditions and high power will also spot a multitude of small craters within and along Furnerius’ walls. For binocular viewers, try spotting crater Stevinus to the north and Fraunhofer to the south.

Now let’s go have a look at a star buried in one of the spiral arms of our own galaxy – W Sagittarii…

Located less than a fingerwidth north of Gamma, the tip of the “teapot spout,” W is a Cepheid variable that’s worth keeping an eye on. While its brightness only varies by less than a magnitude, it does so in less than 8 days! Normally holding close to a magnitude 4, nearby field stars will help you correctly assess when minimum and maximum occur. While it’s difficult for a beginner to see such changes, watch it over a period of time. At maximum, it will be only slightly fainter than Gamma to the south. At minimum, it will be only slightly brighter than the stars to its northeast and southwest.

While you watch W go through its changes – think on this: not only is W a Cepheid variable (a standard for distance measurements), but it is also one that periodically changes its shape. Not enough? Then think twice… Because W is also a Cepheid binary. Still not enough? Then you might like to know that recent research points toward W having a third companion as well!

Wednesday, August 22 – On the lunar surface tonight, head to the eastern shore of Mare Nectaris to catch an easily noticed broken black line. This is the western flank of the Pyrenees Mountains which stretch close to 350 kilometers north to south. The black line you see is a good example of a lunar scarp, a feature more like a cliff than a true mountain range. This scarp ends to the north in crater Guttenberg. Just south of Guttenberg, you will find high contrast Santbech.

Although it will be tough to locate with the unaided eye thanks to the Moon, let’s take a closer look at one of the most unsung stars in this region of sky – Eta Sagittarii. This M-class giant star will show a wonderful color contrast to binoculars or scopes, being slightly more orange than the surrounding field. Located 149 light-years away, this irregular variable star is a source of infrared radiation and is a little larger than our own Sun – yet 585 times brighter. At around 3 billion years old, Eta has either expended its helium core or just begun to use it to fuse carbon and oxygen – creating an unstable star capable of changing its luminosity by about 4%. But have a closer look… For Eta is also a binary system with an 8th magnitude companion!

Thursday, August 23 – Do you remember a few days ago in history when Lunar Orbiter 1 was launched? Well, on this day in history it made headlines as it sent back the very first photo of Earth seen from space!

On the lunar surface tonight, we’ll return to identify Metius, Fabricus and Janssen to the south. Southwest of this trio you will see a sharply defined small crater known as Vlacq. Power up to resolve its small central mountain peak. Angling off to the west and extending westward is multiple crater Hommel. Look especially for Hommel A and Hommel C which fit nicely and precisely within the borders of the older crater. Note how many individual craters make up its borders. Just north of Hommel is Pitiscus and to its south is Nearch.

Now let’s have a look at the brightest star in the “Archer” – Epsilon Sagittarii. Known as Kaus Australis, or the “Southern Bow,” Epsilon holds a respectable magnitude 1.8 and is located around 120 light-years from Earth. This sparkling blue/white star is 250 times brighter than our own Sun. While a major challenge would be to spot Epsilon’s 14th magnitude companion star located about 32? away, even the smallest of telescopes and most binoculars can try for the 7th magnitude visual companion widely spaced to the north-northwest.

Friday, August 24 – Today in 1966 from an Earth-orbiting platform, the Luna 11 mission was launched on a three day trip. After successfully achieving orbit, the mission went on to study many things, including lunar composition and nearby meteoroid streams.

Tonight’s prominent lunar features are also Astronomical League challenges. Look southwest of previous study Theophilus for the huge form of Maurolycus. Its cratered floor may be either partially lit or fully disclosed depending on your observing time. Note especially Maurolycus’ multiple central mountains. North of Maurolycus you will see the well-eroded remains of Gemma Frisius. Its broken walls will show well under current illumination. Finally look carefully for crater Goodacre which has destroyed Gemma Frisius’ northern wall.

The Moon is now becoming the “highlight” of the night sky. Try using “higher power” to diminish some of its glare. While southwestern Sagittarius is also high, why not observe some of its other globular clusters?

Center the scope on Epsilon and sweep less than 3 degrees north-northeast to find small 7.7 magnitude globular M69 (Right Ascension: 18 : 31.4 – Declination: -32 : 21). M69 gives an appearance similar to that of other compact clusters – such as M28 and M80. Small and moderately bright, it appears coarsely textured through smaller instruments and requires larger scopes to bring out its brightest 14th magnitude members. This cluster sits near a blue 7th magnitude star which complicates seeing M69 through binoculars and finderscopes.

Now head a little more than a degree southeast, then north of a pair of 6th magnitude stars to locate NGC 6652 (Right Ascension: 18 : 35.8 – Declination: -32 : 59) – a very small 9th magnitude globular. Go less than 2 degrees northeast to find brighter (8.1 magnitude), larger M70 (Right Ascension: 18 : 43.2 – Declination: -32 : 18). Notice how more of M70?s light is concentrated in its core than M69. Continuing a little more than 3 degrees in the direction of Zeta we encounter M54 (Right Ascension: 18 : 55.1 – Declination: -30 : 29). Through a modest scope, this 7.7 magnitude globular is small, very blue, and intensely concentrated at the core. Larger amateur instruments will only bring out a few 15th magnitude members out of this globular’s faintly glowing form.

Charles Messier discovered M69 and M70 on August 31, 1780 from Paris while trying to confirm a discovery made by Lacaille using a half-inch spyglass in South Africa. These two globulars lie within 2,000 light-years of each other and less than 30,000 light-years from Earth. Due to unusual richness in metal content – for astronomers, “metals” are any elements other than hydrogen and helium – M69 may be a relatively young cluster. At some 90,000 light-years, M54 is the most distant Messier globular cluster – and may not be a globular at all – but the core of a dwarf galaxy beyond the bounds of the Milky Way! In fact M54 is intrinsically larger (300 light-years in diameter) and brighter (magnitude 10.1) than any other globular within the Milky Way itself.

Saturday, August 25 – Tonight the waxing Moon’s most notable features will be the vast area of craters dominating the south-central portion near and along the terminator. Now emerging is Ptolemaeus – just north-northeast of Albategnius. This large round crater is a mountain walled plain filled with lava flow. With the exception of interior crater Ptolemaeus A, binoculars will see it as very smooth. Telescopes however can reveal faint mottling in the surface of the crater’s interior, along with a single elongated craterlet to the northeast. Despite its apparent uniformity, close inspection has revealed as many as 195 interior craterlets within Ptolemaeus! Look for a variety of interior ridges and shallow depressions.

With the moonlight causing studies to be mildly hampered, our main feature for tonight will definitely improve once the Moon sets – so while we’re waiting, let’s drop by open cluster M29 (Right Ascension: 20 : 23.9 – Declination: +38 : 32) less than 2 degrees south-southeast of Gamma Cygni. At lower power, or through small scopes, its handful of brightest members makes this 6.6 magnitude open cluster look more like an asterism than a real group. Lacking any sense of a core, higher power and larger scopes will bring out another dozen or so stars. Those with binoculars will enjoy seeing a few of M29?s brightest stars against a vague nebulosity.

Now let’s see what the “I” can “C”… Less than 2 degrees southwest of M29 (just south of 5th magnitude P Cygni) lies another open cluster of similar brightness and size to M29 – IC 4996 (Right Ascension: 20 – : 16.5 – Declination: +37 : 38). How do these two compare? The less conspicuous IC 4996 lies in a richer Milky Way field and consists of fewer and more compact bright stars. Smaller scopes see this one as a patch of nebulosity.

Now for M55 (Right Ascension: 19 : 40.0 – Declination: -30 : 58). Found in the far reaches of eastern Sagittarius, and west-southwest of Zeta, M55 is one of the coarsest globulars known. At magnitude 7.0, M55 can be seen as a large pale ghost of luminosity in binoculars or finderscopes. This is one very open globular cluster! A multitude of fine, easily resolved stars spread oblately over the mid-power field. Long exposure photos show this to be a true globular glowing with the combined light of almost 100,000 suns.

Tonight is also the peak of the Northern Iota Aquarid meteor shower. While the Moon will totally interfere most of the evening, you still might catch a bright streak!

Sunday, August 26 – The most outstanding feature tonight on the Moon will be a southern crater near the terminator – Maurolycus. Depending on your viewing time, the terminator may be running through it. These shadows will multiply its contrast many times over and display its vivid formations. As true lunar challenge, Maurolycus will definitely catch your eye with its black interior and western crest stretched over the terminator’s darkness. Too many southern craters to be sure? Don’t worry. Maurolycus dominates them all tonight. Look for its double southern wall and multiple crater strikes along its edges. Maurolycus is found about two Crisium lengths southwest of Theophilus and in tonight’s light will appear especially fine. But look just north of Maurolycus to pick out the battered remains of Class III crater Gemma Frisius, another lunar challenge. Spanning 56 miles and descending 17,100 feet below the Moon’s surface, you’ll find its walls broken, yet enough of its northern boundary remains to clearly reveal the impact that created Goodacre. Look for the shadows which blend Goodacre and Gemma Frisius together.

On this date in 1981, Voyager 2 made a fly-by of Saturn. Eight years later in 1989, Voyager 2 flew by Neptune on this date. Why don’t we make a “date” tonight to have a look at this distant blue world? You’ll find it on the ecliptic plane. While large binoculars can pick up Neptune’s very tiny blue orb, you’ll need a telescope tonight to spot it through the lunar glare.

Until next week? Wishing you clear skies!

Posted on by Tammy Plotner

Weekly SkyWatcher’s Forecast: August 13-19, 2012

Greetings, fellow SkyWatchers! Even if you missed the peak of the Perseid meteor shower, there will still be plenty of “strays” to sparkle this week’s dark nights. For astronomy without a telescope, be sure to check out all the planetary alignments – and tell your friends! When you’re ready to learn more about what to view and when this week, then meet me in the back yard…

Monday, August 13 – Celestial scenery alert! If you’re out before dawn this morning, look for the very close pairing of Venus and the slender crescent Moon. For viewers in the north-eastern Asia area, this is an occultation event, so be sure to check resources for times and locations in your area! How about some more eye candy? Then check out the splendid alignment of Saturn, Mars and Spica just after sky dark. Look for the blue/white star to the west, accompanied by red Mars to the east and yellow Saturn even higher to the east. The trio will be roughly separated by the same distance from each other and the colors will be a welcome sight. Be sure to alert your family and friends to all the celestial action that doesn’t require a telescope today!

Tonight, begin with just your eyes as you gaze about four fingerwidths above the top of the Sagittarius “teapot dome” for an open window on the stars and mighty M24 (Right Ascension: 18 : 18.4 – Declination: -18 : 25)…

This huge, hazy patch of stars is in reality an area of space known as “Baade’s Window” – an area free of obscuring gas and dust. Cataloged by Messier in 1764 as object 24, even small binoculars will reveal the incredible vista of the “Sagittarius Star Cloud.” Although it’s actually not a cluster, but rather a clean view of an area of our own galaxy’s spiral arm, that will not lessen the impact when viewed through a telescope. Spanning a degree and a half of sky, it is one of the few areas in which even a novice can easily perceive areas of dark dust.

For larger telescopes, look for the dim, open cluster NGC 6603 (Right Ascension: 18 : 18.4 – Declination: -18 : 25) in the northeastern position of the Window. There are two very notable dark nebulae, B92 and B93, located in the northern segment as well. Near teardrop shaped B92 and its single central star, you should spot open cluster Collinder 469 and also Markarian 38 south of B93. You’ll find B86 near Gamma Sagittarii . At the southern edge of the star cloud, look for emission nebula IC 1283-1284, along with the reflection nebulae NGC 6589 (Right Ascension: 18 : 16.9 – Declination: -19 : 46) and NGC 6590 (Right Ascension: 18 : 17.0 – Declination: -19 : 53) and open cluster NGC 6595 (Right Ascension: 18 : 17.0 – Declination: -19 : 53). Still up for more? Then head west to see if you can find 12th-magnitude planetary nebula NGC 6567 (Right Ascension: 18 : 13.7 – Declination: -19 : 05).

Even if you don’t accept these challenges, you can still enjoy looking at a 560 light-year swatch of stars from one of the Milky Way’s loving arms! (If you’re out late, look for Mira… It was discovered by Fabricius on this date in 1596.)

Tuesday, August 14 – Celestial scenery alert! Be out just after sunset to catch a splendid stellar and planetary conjunction. To the west you’ll see bright Spica. Just above it, Mars. And just above that? Saturn! The trio are all separated by just a few degrees, so be sure to stop and enjoy!
Your first challenge for tonight will be to venture about three fingerwidths northeast of Lambda Sagittarii to visit a well-known but little visited galactic cluster – M25 (Right Ascension: 18 : 31.6 – Declination: -19 : 15).

First discovered by Cheseaux and then cataloged by Messier, it was observed and recorded by William Herschel, Johann Elert Bode, Admiral Smythe and T. W. Webb…but never added to the NGC catalog of John Herschel! Thanks to J.L.E. Dreyer, it did make the second Index Catalog as IC 4725.

Seen with even the slightest optical aid, this 5th magnitude cluster contains two G-type giants as well as a Delta Cephei-type variable with the designation of U, which changes about one magnitude in a period of less than a week. It’s very old for an open cluster, perhaps near 90 million years, and the light you see tonight left the cluster over 2000 years ago. While binoculars will see around a double handful of bright stars overlaying fainter members, telescopes will reveal more and more as aperture increases. At one time it was believed to have only about 30 members, but this was later revised to 86. But recent studies by Archinal and Hynes indicate it may have as many as 601 member stars!

Wednesday, August 15 – Celestial scenery alert! Get up before dawn to spot Mercury low on the eastern horizon, a very tiny crescent Moon to its west/southwest and brilliant Venus ruling above it all! To add to the mix, you’ll see the pairing of the Gemini Twins – Castor and Pollux – just about a handspan above Mercury and luminous Procyon about the same distance due south. If you missed your opportunity to view Spica, Mars and Saturn on Monday, don’t worry. The colorful trio is still around tonight just after sky dark to the west, but now you can see that Mars has moved slightly to the south. Ain’t celestial mechanics grand?!

Tonight we’ll head back to Scorpius to have a look at three pristine open clusters. Begin your starhop at the colorful southern Zeta pair and head north less than one degree for NGC 6231 (Right Ascension: 16 : 54.0 – Declination: -41 : 48).

Wonderfully bright in binoculars and well resolved to the telescope, this tight open cluster was first discovered by Hodierna before 1654. De Cheseaux cataloged it as object 9, Lacaille as II.13, Dunlop as 499, Melotte as 153, and Collinder as 315. No matter what catalog number you chose to put in your notes, you’ll find the 3.2 million year young cluster shining as the “Northern Jewelbox!” For high power fans, look for the brightest star in this group – it’s van den Bos 1833, a splendid binary.

About another degree north is loose open cluster Collinder 316, with its stars scattered widely across the sky. Caught on its eastern edge is another cluster known as Trumpler 24, a site where new variables might be found. This entire region is encased in a 90 arc minute faint emission nebula called IC 4628 (Right Ascension: 16 : 57.0 – Declination: -40 : 20) – making this low power journey through southern Scorpius a red hot summer treat!

Thursday, August 16 – If you did not get a chance to look at the Northern Jewelbox region in Scorpius, return again and sweep the area tonight. For those with larger telescopes, we’re going to hop about a degree and a half south of twin Nu for NGC 6242 (Right Ascension: 16 : 55.6 – Declination: -39 : 30).

Discovered by Lacaille and cataloged as I.4, it is also known as Dunlop 520, Melotte 155 and Collinder 317. At roughly magnitude 6, this open cluster is within binocular range, but truly needs a telescope to appreciate its fainter stars. While NGC 6242 might seem like nothing more than a pretty little cluster with a bright double star, it contains an x-ray binary which is a “runaway” black hole. It is surmised that it formed near the galactic center and was vaulted into an eccentric orbit when the progenitor star exploded. Its kinetic energy is much like a neutron star or a millisecond pulsar, and it was the first black hole confirmed to be in motion.

Now head a little more than a degree east-southeast for NGC 6268 (Right Ascension: 17 : 02.4 – Declination: -39 : 44). At a rough magnitude of 9, this small open cluster can be easily observed in smaller scopes and resolved in larger ones. The cluster itself is somewhat lopsided, with more of its members concentrated on the western half of its borders. While it, too, might not seem particularly interesting, this young cluster is highly evolved and contains some magnetic, chemically peculiar stars and Be class, or metal-weak, members.

Friday, August 17 – Today in 1966 Pioneer 7 was launched. It was the second in a series of satellites sent to monitor the solar wind, and study cosmic rays, interplanetary space, and magnetic fields. If you’re out early, be sure to take a look for the close pairing of Mars and Saturn and Spica. If you’ve had the opportunity to view them over the last few days, you can see how quickly Mars has moved! Instead of being in a line, the trio now… well… triangulates!

Tonight it’s New Moon! Let’s return to previous study star Lambda Scorpii and hop three fingerwidths northeast… We’re re-hunting the “Butterfly!”

Easily seen in binoculars and tremendous in the telescope, this brilliant magnitude 4 open cluster was first discovered by Hodierna before 1654 and independently discovered by de Cheseaux as his object 1, before being cataloged by Messier as M6 (Right Ascension: 17 : 40.1 – Declination: -32 : 13). Containing around 80 stars, the light you see tonight left its home in space around the year 473 A.D. It is believed to be around 95 million years old and contains a single yellow supergiant – the variable BM Scorpii. While most of M6?s stars are hot, blue main sequence, the unique shape of this cluster gives it not only visual appeal, but wonderful color contrast as well!

Now let’s head towards more unusual open clusters – this time in Cygnus. Starting with Gamma Cygni, locate a loose cluster involving Gamma, Do (Dolidze) 43. Now shift two degrees southwest to pick up Do 42 as well. Don’t confuse Do 42 with nearby M29 though, for the two look very similar. For fans of the “Double Cluster” in Perseus, you’ll like the next pairing! Shift another half degree southwest along the body of Cygnus to pick out Do 40 and Do 41. This pretty pair can be placed in the same low power field. By moving another half degree due west, you’ll find highly populated Do 39 and that, too, is a double treat. The brighter clump of stars in the same low power field is IC 4996 (Right Ascension: 20 : 16.5 – Declination: +37 : 38).

Now for two bright open clusters. The first, Ruprecht 173 is about a degree northwest of Epsilon Cygni. You’ll truly appreciate this heavily populated star cluster! The next is as easy as identifying the constellation of Lyra. Just southeast of bright Vega is a wonderful double for binoculars, Delta 1 and 2 – the easternmost most two stars in the lyre. This bright pair is part of an open cluster known as Stephenson 1.

Saturday, August 18 – On this day in 1868, Norman Lockyer was very busy as he was the first to see helium absorption lines in the Sun’s spectrum. Tonight we’ll take a walk from helium rich Lambda Scorpii about three fingerwidths east-northeast to an even more prominent area of stars that was known to Ptolemy as far back as 130 AD.

Astronomers throughout the ages have spent time with this cluster: Hodierna as Ha II.2; Halley in 1678 as number 29, Derham in 1733 as number 16, De Cheseaux as number 10, Lacaille as II.14; Bode as 41; once for William Herschel and again for John as h 3710; Dreyer as NGC 6475… But we know it best as Messier Object 7 (Right Ascension: 17 : 53.9 – Declination: -34 : 49).

Set against the backdrop of the Milky Way, even the smallest of binoculars will enjoy this bright open cluster while telescopes can resolve its 80 members. Roughly 800 light-years away, it contains many different spectral types in various stages of evolution, giving the cluster an apparent age of about 260 million years. Full of binaries and close doubles, an extreme test of tonight’s lighting conditions would be to see if you can spot the 11th magnitude globular cluster NGC 6453 (Right Ascension: 17 : 50.9 – Declination: -34 : 36) to the northwest!

And for last, the densely populated open cluster M11 (Right Ascension: 18 : 51.1 – Declination: -06 : 16). The “Wild Duck” cluster soars about a fist’s width northeast of M16. Dominated by a single 8th magnitude star, this conically-shaped 3,000 member assembly of stardust easily resolves into innumerable stars with any significant amount of magnification. Through intermediate aperture, this 6000 light-year distant, 250 million year old cluster takes on a new form as several hundred 13th and 14th magnitude members begin to spill outside its V-shaped bounds! Discovered by Gottfried Kirch of Berlin observatory in 1681, the cluster was first noted as stellar by William Derham in the first third of the 18th century. Charles Messier added it to his catalog May 30, 1764.

Sunday, August 19 – Born today in 1646, let’s have a look at John Flamsteed. He was an English astronomer with a passion for what he did. Despite a rather difficult childhood and no formal education, he went on to become the First Observer at the Royal Observatory and his catalog of 3000 stars was perhaps the most accurate yet published. Flamsteed star numbers are still in use. Also born on this day was Orville Wright, in 1871, and in 1891, Milton Humason, a colleague of Edwin Hubble at Mts. Wilson and Palomar. The latter was instrumental in measuring the faint spectra of galaxies, which in turn provided evidence for the expansion of the Universe.

This would be a great time for us to have a look at one of the summer’s most curious galaxies – NGC 6822 (Right Ascension: 19 : 44.9 – Declination: -14 : 48). This study is a telescopic challenge even for skilled observers. Set your sights roughly 2 degrees northeast of easy double 54 Sagittarii, and have a look at this distant dwarf galaxy bound to our own Milky Way by invisible gravitational attraction…

Named after its discoverer (E. E. Barnard – 1884), “Barnard’s Galaxy” is a not-so-nearby member of our local galaxy group. Discovered with a 6? refractor, this 1.7 million light-year distant galaxy is not easily found, but can be seen with very dark sky conditions and at the lowest possible power. Due to large apparent size, and overall faintness (magnitude 9), low power is essential in larger telescopes to give a better sense of the galaxy’s frontier. Observers using large scopes will see faint regions of glowing gas (HII regions) and unresolved concentrations of bright stars. To distinguish them, try a nebula filter to enhance the HII and downplay the star fields. Barnard’s Galaxy appears like a very faint open cluster overlaid with a sheen of nebulosity, but the practiced eye using the above technique will clearly see that the “shine” behind the stars is extragalactic in nature.

Now look less than a degree north-northwest to turn up pale blue-green NGC 6818 (Right Ascension: 19 : 44.0 – Declination: -14 : 09) – the “Little Gem” planetary. Easily found in any size scope, this bright and condensed nebula reveals its annular nature in larger scopes but hints at it in scopes as small as 6?. Use a super wide field long-focus eyepiece to frame them both!

Until next week? Wishing you clear skies!

Posted on by Tammy Plotner

Weekly SkyWatcher’s Forecast: August 6-12, 2012

Globular Cluster M15 from Hubble - Credit: ESA, Hubble, NASA

Greetings, fellow SkyWatchers! While you start your observing week out by watching the Mars Curiosity Landing, be sure to step outside and view the Aquarid meteor shower, too! It’s going to be a grand week for globular cluster studies and breezing along the Milky Way. Whenever you’re ready to learn some more history, mystery and just plain fun things about the night sky, then meet me in the back yard.

Monday, August 6 – Today in 2001 the Galileo spacecraft made its flyby of Jupiter’s moon – Io -sending back incredible images of the surface. For southern hemisphere observers, be on watch as the Iota Aquarid meteor shower peaks on this Universal date.

Tonight our studies of globular clusters continues as we look deeper into structure. As a rule, globular clusters normally contain a large number of variable stars, and most are usually the RR Lyrae type such as in earlier study M54. At one time they were known as “cluster variables,” with their number differing from one globular to another. Many globulars also contain vast numbers of white dwarfs. Some have neutron stars which are detected as pulsars, but out of all 151, only four have planetary nebulae in them.

Now, let us head toward the emerging constellation of Pegasus and the magnitude 6.5, class IV M15 (Right Ascension: 21 : 30.0 – Declination: +12 : 10). Easily located with even small binoculars about four degrees northwest of Enif, this magnificent globular cluster is a true delight in a telescope. Amongst the globulars, M15 ranks third in variable star population with 112 identified. As one of the densest of clusters, it is surprising that it is considered to be only class III. Its deeply concentrated core is easily apparent, and has begun the process of core collapse. The central core itself is very small compared to the cluster’s true size and almost half M15?s mass is contained within it. Although it has been studied by the Hubble, we still do not know if this density is caused by the cluster stars’ mutual gravity, or if it might disguise a supermassive object similar to those in galactic nuclei.

M15 was the first globular cluster in which a planetary nebula, known as Pease 1, could be identified. Larger aperture scopes can easily see it at high power. Surprisingly, M15 also is home to 9 known pulsars, which are neutron stars left behind from previous supernovae during the cluster’s evolution, and one of these is a double neutron star. While total resolution is impossible, a handful of bright stars can be picked out against that magnificent core region and wonderful chains and streams of members await your investigation tonight!

Tuesday, August 7 – On this date in 1959, Explorer 6 became the first satellite to transmit photographs of the Earth from its orbit.

Tonight, let’s return again to look at two giant globular clusters roughly equal in size, but not equal in class. To judge them fairly, you must use the same eyepiece. Start first by re-locating previous study M4. This is a class IX globular cluster. Notice the powder-like qualities. It might be heavily populated, but it is not dense. Now return to previous study M13. This is a class V globular cluster. Most telescopes will make out at least some resolution and a distinct core region. It is the level of condensation that determines the class. It is no different from judging magnitudes and simply takes practice.

Try your hand at M55 (Right Ascension:19 : 40.0 – Declination: -30 : 58) along the bottom of the Sagittarius “teapot” – it’s a class XI. Although it is a full magnitude brighter than class I M75, which we looked at earlier in the week, can you tell the difference in concentration? For those with GoTo systems, take a quick hop through Ophiuchus and look at the difference between NGC 6356 (class II) and NGC 6426 (class IX). If you want to try one that they can’t even classify? Look no further than M71 (Right Ascension: 19 : 53.8 – Declination: +18 : 47) in Sagitta. It’s all a wonderful game and the most fun comes from learning!

In the meantime, don’t forget all those other wonderful globular clusters such as 47 Tucanae, Omega Centauri, M56, M92, M28 and a host of others!

Wednesday, August 8 – Today in 2001, the Genesis Solar Particle Sample Return mission was launched. In September of 2004, it crash landed in the Utah desert with its precious payload. Although some of the specimens were contaminated, some did survive the mishap. So what is “star stuff?” Mostly highly charged particles generated from a star’s upper atmosphere and flowing out in a state of matter known as plasma…

Tonight let’s study one of the grandest of all solar winds as we seek out an area about three fingerwidths above the Sagittarius “teapot’s spout” as we have a look at magnificent M8 (Right Ascension: 18 : 03.8 – Declination: -24 : 23), the “Lagoon Nebula.”

Visible to the unaided eye as a hazy spot in the Milky Way, fantastic in binoculars, and an area truly worth study in any size scope, this 5200 light-year area of emission, reflection and dark nebulae has a rich history. Its involved star cluster – NGC 6530 – was first discovered by Flamsteed around 1680, and the nebula by Le Gentil in 1747. Cataloged by Lacaille as III.14 about 12 years before Messier listed it as number 8, its brightest region was recorded by John Herschel and the dark nebulae were discovered by Barnard.

Tremendous areas of starbirth are taking place in this region; while young, hot stars excite the gases in a are known as the “Hourglass,” around Herschel star 36 and 9 Sagittarius. Look closely around cluster NGC 6530 for Barnard dark nebulae B89 and B296 at the nebula’s southern edge. No matter how long you chose to swim in the “Lagoon” you will sure find more and more things to delight both the mind and the eye!

Thursday, August 9 – Today in 1976, the Luna 24 mission was launched on a return mission of its own – not to retrieve solar winds samples, but lunar soil! Remember this mission as we take a look at its landing site in the weeks ahead.

Tonight we’ll return to the nebula hunt as we head about a fingerwidth north and just slightly west of M8 for the “Trifid”…

M20 (Right Ascension: 18 : 02.3 – Declination: -23 : 02) was discovered by Messier on June 5, 1764, and much to his credit, he described it as a cluster of stars encased in nebulosity. This is truly a wonderful observation since the Trifid could not have been easy given his equipment. Some 20 years later William Herschel (although he usually avoided repeating Messier objects) found M20 of enough interest to assign separate designations to parts of this nebula – IV.41, V.10, V.11, V.12. The word “Trifid” was used to describe its beauty by John Herschel.

While M20 is a very tough call in binoculars, it is not impossible with good conditions to see the light of an area that left its home nearly a millennium ago. Even smaller scopes will pick up this round, hazy patch of both emission and reflection, but you will need aversion to see the dark nebula which divides it. This was cataloged by Barnard as B85. Larger telescopes will find the Trifid as one of the very few objects that actually appears much in the eyepiece as it does in photographs – with each lobe containing beautiful details, rifts and folds best seen at lower powers. Look for its cruciform star cluster and its fueling multiple system while you enjoy this triple treat tonight!

Friday, August 10 – Today in 1966 Lunar Orbiter 1 was successfully launched on its mission to survey the Moon. In the weeks ahead, we’ll take a look at what this mission sent back!

Tonight we’ll look at another star forming region as we head about a palm’s width north of the lid star (Lambda) in the Sagittarius teapot as we seek out “Omega”…

Easily viewed in binoculars of any size and outstanding in every telescope, the 5000 light-year distant Omega Nebula was first discovered by Philippe Loys de Cheseaux in 1745-46 and later (1764) cataloged by Messier as object 17. This beautiful emission nebula is the product of hot gases excited by the radiation of newly born stars. As part of a vast region of interstellar matter, many of its embedded stars don’t show in photographs, but reveal themselves beautifully to the eye of the telescope. As you look at its unique shape, you realize that many of these areas are obscured by dark dust, and this same dust is often illuminated by the stars themselves.

Often known as the “Swan,” M17 (Right Ascension: 18 : 20.8 – Declination: -16 : 11) will appear as a huge, glowing check mark or ghostly “2? in the sky – but power up if you use a larger telescope and look for a long, bright streak across its northern edge, with extensions to both the east and north. While the illuminating stars are truly hidden, you will see many glittering points in the structure itself and at least 35 of them are true members of this region spanning about 40 light-years that could contain up to 800 solar masses. It is awesome…

Saturday, August 11 – On this date in 1877, Asaph Hall of the U.S. Naval Observatory was very busy. This night would be the first time he would see Mars’ outer satellite Deimos! Six nights later, he observed Phobos, giving Mars its grand total of two moons.

Tonight after midnight is the peak of the Perseid meteor shower, and this year there’s not so much Moon to contend with! Now let’s sit back and talk about the Perseids while we watch…

The Perseids are undoubtedly the most famous of all meteor showers and never fail to provide an impressive display. Their activity appears in Chinese history as far back as 36 AD. In 1839, Eduard Heis was the first observer to give an hourly count, and discovered their maximum rate was around 160 per hour at that time. He, and other observers, continued their studies in subsequent years to find that this number varied.

Giovanni Schiaparelli was the first to relate the orbit of the Perseids to periodic comet Swift-Tuttle (1862 III). The fall rates have both risen and fallen over the years as the Perseid stream was studied more deeply, and many complex variations were discovered. There are actually four individual streams derived from the comet’s 120 year orbital period which peak on slightly different nights, but tonight through tomorrow morning at dawn is our accepted peak.

Meteors from this shower enter Earth’s atmosphere at a speed of 60 km/sec (134,000 miles per hour), from the general direction of the border between the constellations Perseus and Cassiopeia. While they can be seen anywhere in the sky, if you extend their paths backward, all the true members of the stream will point back to this region of the sky. For best success, position yourself so you are generally facing northeast and get comfortable. If you are clouded out, don’t worry. The Perseids will be around for a few more days yet, so continue to keep watch!

And speaking of watching… If you’re out late, be sure to watch for a Jupiter/Moon conjunction. What an inspiring bit of sky scenery to watch them rise together! For lucky viewers in the Indonesia area, this is an occultation event, so please be sure to check resources for times and locations in your area.

Sunday, August 12 – Did you mark your calendar to be up before dawn to view the Perseid meteor shower? Good!

Tonight while dark skies are on our side, we’ll fly with the “Eagle” as we hop another fingerwidth north of M17 and head for one of the most famous areas of starbirth – IC 4703.

While the open cluster NGC 6611 was first discovered by Cheseaux in 1745-6, it was Charles Messier who cataloged the object as M16 and he was the first to note the nebula IC 4703 (Right Ascension: 18 : 18.9 – Declination: -13 : 47), more commonly known as the “Eagle.” At 7000 light-years distant, this roughly 7th magnitude cluster and nebula can be spotted in binoculars, but at best it is a hint. As part of the same giant cloud of gas and dust as neighboring M17, the Eagle is also a place of starbirth illuminated by these hot, high energy stellar youngsters which are only about five and a half million years old.

In small to mid-sized telescopes, the cluster of around 20 brighter stars comes alive with a faint nebulosity that tends to be brighter in three areas. For larger telescopes, low power is essential. With good conditions, it is very possible to see areas of dark obscuration and the wonderful “notch” where the Pillars of Creation lie. Immortalized by the Hubble Space telescope, you won’t see them as grand or colorful as it did, but what a thrill to know they are there!

Until next week? Clear skies!

Posted on by Tammy Plotner

Weekly SkyWatcher’s Forecast: July 30 – August 5, 2012

Greetings, fellow SkyWatchers! It’s big. It’s bright. There’s no escaping it. This week the Moon will be our major point of study, but don’t rule out some bright globular clusters and interesting stars! There’s plenty of history and science to explore, too. Whenever you’re ready, just meet me in the back yard…

Monday, July 30 – Today’s history celebrates the 2001 flyby of the Moon by the Wilkinson Microwave Anisotropy Probe (WMAP) on its way to Lagrange Point 2 to study the cosmic microwave background radiation.

Now that we’re back at Sinus Iridum on the lunar surface, we’ll hop across Mare Frigoris and northeast of the punctuation of Harpalus for a grand old crater – J. Herschel. Although it looks small because it is seen on the curve, this wonderful old walled plain named for John Herschel contains some very tiny details. Its southeastern rim forms the edge of Mare Frigoris and the small (24 km) Horrebow dots its southwest edge. The crater walls are so eroded with time that not much remains of the original structure. Look for many very small telescopic impact craters which dot J. Herschel’s uneven basin and exterior edges. Power up! If you can spot the small central crater C, you are resolving a feature only 12 kilometers wide from some 385,000 kilometers away! Formed in the Pre-Nectarian period, this walled plain could be as much as 4 billion years old…

Now, relax and enjoy the peak of the Capricornid meteor shower. Although it is hard for the casual observer to distinguish these meteors from the Delta Aquarids, no one minds. Again, face southeast and enjoy! The fall rate for this shower is around 10 to 35 per hour, but unlike the Aquarids, this stream produces those great “fireballs” known as bolides. Enjoy…

Tuesday, July 31 – Tonight on the Moon, look south of Mare Humorum is darker Paulus Epidemiarum eastward and paler Lacus Excellentiae westward. To their south you will see a complex cojoined series of craters we’ll take a closer look at – Hainzel and Mee. Hainzel was named for Tycho Brahe’s assistant and measures about 70 kilometers in length and sports several various interior wall structures. Power up and look. Hainzel’s once high walls were obliterated on the north-east by the strike that caused Hainzel C and to the north by impact which caused the formation of Hainzel A. To its basic south is eroded Mee – named for a Scottish astronomer. While Crater Mee doesn’t appear to be much more than simple scenery, it spans 172 kilometers and is far older than Hainzel. While you can spot it easily in binoculars, close telescope inspection shows how the crater is completely deformed by Hainzel. Its once high walls have collapsed to the northwest and its floor is destroyed. Can you spot small impact crater Mee E on the northern edge?

Now, let’s take the opportunity to look at two multiple star systems – Nu and Xi Scorpii.

Starting with Nu about a fingerwidth east and slightly north of bright Beta, we find a handsome duo of stars in a field of nebulosity that will challenge telescopic observers much the way that Epsilon Lyrae does. With any small telescope, the observer will easily see the widely separated A and C stars. Add just a little power and take your time… The C star has a D companion to the southwest! For larger telescopes, take a very close look at the primary star. Can you separate the B companion to the south?

Now let’s hop to Xi about four fingerwidths north of Beta.

Discovered by Sir William Herschel in 1782, this 80 light-year distant system poses a nice challenge for mid-sized scopes. The yellow-hued A and B pair share a very eccentric orbit about the same distance as Uranus is from our Sun. During the 2007 observing year they should be fairly well spaced, and the slightly fainter secondary should appear to the north. Look a good distance away for the 7th magnitude orange C component and south for yet another closely-matched double of 7th and 8th magnitude – the D and E stars.

For the larger scope, this multiple star system does display a little bit of color. Most will see the A and B components as yellow/white, the C star as slightly orange, and the D/E pair as slightly tinged with blue. Be sure to mark your observations for this is one of the finest!

Wednesday, August 1 – Today is the birthdate of Maria Mitchell. Born in 1818, Mitchell became the first woman to be elected as an astronomer to the American Academy of Arts and Sciences. She later rocketed to worldwide fame when she discovered a bright comet in 1847.

For larger telescopes, let’s try a challenging lunar study worthy of your observing skills. Due west of Hansteen you will find a small crater known as Sirsalis near the terminator. It will appear as a small, dark ellipse with a bright west wall along with its twin, Sirsalis B. The feature you will be looking for is the Sirsalis Rille – the longest lunar “wrinkle” presently known. Stretching northeast of Sirsalis and ex-tending 459 kilometers south to the bright rays of Byrgius, this major “crack” in the lunar surface shows several branchings – like a long dry river bed. Geologically forming in the Imbrian period, chances are the Sirsalis Rille is lunar graben. Thanks to Lunar Orbiter images, the evidence points to shifting tectonic plates as the source of this incredible feature.

Tonight, let’s continue our exploration of globular clusters. These gravitationally bound concentrations of stars contain anywhere from ten thousand to one million members and attain sizes of up to 200 light-years in diameter. At one time, these fantastic members of our galactic halo were believed to be round nebulae. Perhaps the very first to be discovered was M22 in by Abraham Ihle in 1665. This particular globular is easily seen in even small binoculars and can be located just slightly more than two degrees northeast of the “teapot’s lid,” Lambda Sagittarii.

Ranking third amongst the 151 known globular clusters in total light, M22 (Right Ascension: 18 : 36.4 – Declination: -23 : 54) is probably the nearest of these incredible systems to our Earth with an approximate distance of 9600 light-years, and it is also one of the nearest globulars to the galactic plane. Since it resides less than a degree from the ecliptic, it often shares the same eyepiece field with a planet. At magnitude 6, the class VII M22 will begin to show individual stars to even modest instruments and will burst into stunning resolution for larger aperture. About a degree west-northwest, mid-sized telescopes and larger binoculars will capture smaller 8th magnitude NGC 6642. At class V, this particular globular will show more concentration toward the core region than M22. Enjoy them both!

Thursday, August 2 – Tonight we’ll fly right by the Full Buck Moon as we continue our studies to have a look at Mu 1 and Mu 2 Scorpii about two fingerwidths north of Zeta.

Very close to the same magnitude and spectral type, the twin Mu stars are easy to separate visually and most definitely worth a look in telescopes or binoculars. They are considered an actual physical pair because they share the exact same distance and proper motion, but they are separated by less than one light-year.

Hanging out in space some 520 light-years away, western Mu 1 is a spectroscopic binary – the very first discovered to have double lines. This Beta Lyrae-type star has an orbiting companion that eclipses it around every day and a half, yet causes no significant visual drop in magnitude – even though the orbiting companion is only 10 million kilometers away from it! While that sounds like plenty of distance, when the two pass, their surfaces would nearly touch each other!

Friday, August 3 – Tonight let’s race ahead of the rising Moon as we continue our studies with one of the globulars nearest to the galactic center – M14 (Right Ascension: 17 : 37.6 – Declination: -03 : 15). Located about sixteen degrees (less than a handspan) south of Alpha Ophiuchi, this ninth magnitude, class VIII cluster can be spotted with larger binoculars, but will only be fully appreciated with the telescope.

When studied spectroscopically, globular clusters are found to be much lower in heavy element abundance than stars such as own Sun. These earlier generation stars (Population II) began their formation during the birth of our galaxy, making globular clusters the oldest of formations that we can study. In comparison, the disk stars have evolved many times, going through cycles of starbirth and supernovae, which in turn enrich the heavy element concentration in star forming clouds and may cause their collapse. Of course, as you may have guessed, M14 breaks the rules. It contains an unusually high number of variable stars – in excess of 70 – with many of them known to be the W Virginis type. In 1938, a nova appeared in M14, but it was undiscovered until 1964 when Amelia Wehlau of the University of Ontario was surveying the photographic plates taken by Helen Sawyer Hogg. The nova was revealed on eight of these plates taken on consecutive nights, and showed itself as a 16th magnitude star – and was believed to be at one time almost 5 times brighter than the cluster members. Unlike 80 years earlier with T Scorpii in M80, actual photographic evidence of the event existed. In 1991, the eyes of the Hubble were turned its way, but neither the suspect star nor traces of a nebulous remnant were discovered. Then six years later, a carbon star was discovered in M14.

To a small telescope, M14 will offer little to no resolution and will appear almost like an elliptical galaxy, lacking in any central condensation. Larger scopes will show hints of resolution, with a gradual fading towards the cluster’s slightly oblate edges. A true beauty!

Saturday, August 4 – As we explore globular clusters, we simply assume them all to be part of the Milky Way galaxy, but that might not always be the case. We know they are basically concentrated around the galactic center, but there may be four of them that actually belong to another galaxy. Tonight we’ll look at one such cluster being drawn into the Milky Way’s halo. Set your sights just about one and a half degrees west-southwest of Zeta Sagittarii for M54 (Right Ascension: 18 : 55.1 – Declination: -30 : 29).

At around magnitude 7.6, M54 is definitely bright enough to be spotted in binoculars, but its rich class III concentration is more notable in a telescope. Despite its brightness and deeply concentrated core, M54 isn’t exactly easy to resolve. At one time we thought it to be around 65,000 light-years distant, and rich in variables – with 82 known RR Lyrae types. We knew it was receding, but when the Sagittarius Dwarf Elliptical Galaxy was discovered in 1994, it was noted that M54 was receding at almost precisely the same speed! When more accurate distances were measured, we found M54 to coincide with the SagDEG distance of 80-90,000 light-years, and M54?s distance is now calculated to be 87,400 light-years. No wonder it’s hard to resolve – it’s outside our galaxy!

As we know, most globular clusters congregate around the galactic center in the Ophiuchus/Sagittarius region. Tonight let’s explore what creates a globular cluster’s form… We’ll start with the “head of the class,” M75 (Right Ascension: 20 : 06.1 – Declination: -21 : 55).

Orbiting the galactic center for billions of years, globular clusters endured a wide variety of disturbances. Their component stars escape when accelerated by mutual encounters and the tidal force of our own Milky Way pulls them apart when they are near periapsis, that is, closest to the galactic center. Even close encounters with other masses, such as other clusters and nebulae, can affect them! At the same time, their stellar members are also evolving and this loss of gas can contribute to mass loss and deflation of these magnificent clusters. Although this happens far less quickly than in open clusters, our observable globular friends may only be the survivors of a once larger population, whose stars have been spread throughout the halo. This destruction process is never-ending, and it is believed that globular clusters will cease to exist in about 10 billion years.

Although it will be later evening when M75 appears on the Sagittarius/Capricornus border, you will find the journey of about 8 degrees southwest of Beta Capricorni worth the wait. At magnitude 8, it can be glimpsed as a small round patch in binoculars, but a telescope is needed to see its true glory. Residing around 67,500 light-years from our solar system, M75 is one of the more remote of Messier’s globular clusters. Since it is so far from the galactic center – possibly 100,000 light-years distant – M75 has survived almost intact for billions of years to remain one of the few Class I globular clusters. Although resolution is possible in very large scopes, note that this globular cluster is one of the most concentrated in the sky, with only the outlying stars resolvable to most instruments.

Sunday, August 5 – Today we celebrate the birthday of Neil Armstrong, the first human to walk on the Moon. Congratulations! Also on this date in 1864, Giovanni Donati made the very first spectroscopic observations of a comet (Tempel, 1864 II). His observations of three absorption lines led to what we now know as the Swan bands, from a form of the carbon radical C2.

Our study continues tonight as we move away from the galactic center in search of a remote globular cluster that can be viewed by most telescopes. As we have learned, radial velocity measurements show us the majority of globulars are involved in highly eccentric elliptical orbits, which take them far outside the plane of the Milky Way. These orbits form a sort of spherical “halo” which tends to be more concentrated toward our galactic center. Reaching out several thousands of light-years, this halo is actually larger than the disk of our own galaxy. Since globular clusters aren’t involved in our galaxy’s disk rotation, they may possess very high relative velocities. Tonight let’s head toward the constellation of Aquila and look at one such globular – NGC 7006 (Right Ascension: 21 : 01.5 – Declination: +16 : 11).

Located about half a fist’s width east of Gamma Aquilae, NGC 7006 is speeding towards us at a velocity of around 345 kilometers per second. At 150,000 light-years from the center of our galaxy, this particular globular could very well be an extra-galactic object. At magnitude 11.5, it’s not for the faint of heart, but can be spotted in scopes as small as 150mm, and requires larger aperture to look like anything more than a suggestion. Given its tremendous distance from the galactic center, it’s not hard to realize this is a class I – although it is quite faint. Even the largest of amateur scopes will find it unresolvable!

Until next week? May all your skies by clear and steady…

Lead image caption: Crater J. Herschel – Credit: Damian Peach