Posted on by David Dickinson

Mysterious Moon Flashes: Could the Transient Lunar Phenomena be Linked to the Solar Cycle?

The Moon, our nearest natural satellite. (Photo by author).

A key mystery in observational lunar astronomy may be at least partially resolved.

An interesting study appeared recently in the British Astronomical Association’s (BAA) March 2013 edition of their Lunar Section Circular. The study is one of the most comprehensive looks at possible connections between Transient Lunar Phenomena and the Solar Cycle.

Collection of TLP reports analyzed by Barbara Middlehurst & Sir Patrick Moore. The red dots indicate reddish events, the yellow one other colored events. (Wikimedia Commons image in the Public Domain).
Collection of TLP reports analyzed by Barbara Middlehurst & Sir Patrick Moore. The red dots indicate reddish events. The yellow ones represent other colored events. (Wikimedia Commons image in the Public Domain).

Transient Lunar Phenomena (or TLPs) are observations collected over the years of flashes or glows on the Moon. Since these phenomena often rely on a report made by a solitary observer, they have been very sparsely studied.

The term itself was coined by Sir Patrick Moore in 1968. One of the very earliest reports of a TLP event was the flash seen on the dark limb of the waxing crescent Moon by Canterbury monks in 1178.

Other reports, such as a daylight “star near of the daytime crescent Moon” seen by the residents of Saint-Denis, France on January 13, 1589 was almost certainly a close conjunction of the planet Venus. Bright planets such as Venus can be easily seen next to the Moon in the daytime.

A daytime Moon and Venus as seen from France on January 13th, 1589. (Created by the author in Starry Night).
A daytime Moon and Venus as seen from France on January 13th, 1589. (Created by the author in Starry Night).

A stunning illusion also occurs when the Moon occults, or passes in front of a bright star or planet. In fact, there’s a name for this psychological phenomenon of a bright star seeming to “hang” between the horns of the Moon just prior to an occultation, known as the Coleridge Effect. This takes its name from a line in Coleridge’s Rime of the Ancient Mariner;

“Till clomb above the eastern bar, the horned Moon with one bright star,

Within nether tip.”

Okay, we’ve never seen the “horned Moon clomb,” either. But this does describe a real illusion often seen during an occultation. The mind thinks that gap between the horns of the Moon should be transparent, and the lingering planet or star seems to cross that space on the dark limb, if only for a second. Incidentally, South American residents will get to check this out during the next occultation of Venus this year on September 8th.

So, what does this have to do with the 11-year solar cycle? Well, when you strip away many of the dubious observations of TLPs over the years, a core of well- documented events described by seasoned observers remains. Anyone who has sketched such a complex object as the Moon realizes that fine detail becomes apparent on scrutiny that may be missed in a casual glance. But one persistent assertion that has gone around the astronomical community for years is that an increase in the number of TLP events is linked to the peak of the solar cycle.

This was first suggested in 1945 by H. Percy Wilkins. A later study by Barbara Middlehurst in 1966 disproved the idea, citing no statistical correlation between sunspot activity and TLPs.

Of course, pundits have tried unsuccessfully to link the solar cycle to just about everything, from earthquakes to human activity to booms and busts of the stock market. Most flashes on the dark limb of the Moon are suspected to be meteorite impacts. In fact, the advent of high-speed photography has been able to reveal evidence for lunar strikes during intense meteor showers such as the Leonids and Geminids.

Flash of a Leonid impact captured on the limb of the Moon in 2006. Click image to see animation. (Credit: NASA Meteoroid Environment Office).
Flash of a Leonid impact captured on the limb of the Moon in 2006. Click image to see animation. (Credit: NASA Meteoroid Environment Office).

What’s at little less clear are the source of luminous “hazes” or “glows” noted by observers. Keep in mind; we’re talking subtle effects noted after meticulous study. NASA even commissioned a study of TLPs named Project Moon-Blink during the early Apollo program. About a third of TLP events have been observed near the bright crater Aristarchus. Researchers even managed to get Neil Armstrong to make an observation of the crater during a pass on Apollo 11. He noted that “there’s an area that is considerably more illuminated than the surrounding area. It seems to have a slight amount of fluorescence.”

Aristarchus crater (arrowed) near Full Moon. Note how bright it is compared to the surrounding terrain. (Photo by Author).
A crater with a relatively high albedo (Proclus, arrowed) near Full Moon. Note how bright it is compared to the surrounding terrain. (Photo by Author).

But what’s interesting in the recent BAA study conducted by Jill Scambler is the amount of data that was available. The study was a comprehensive analysis of TLPs noted by the BAA, the Association of Lunar and Planetary Observers (ALPO) and NASA from 1700 to 2010. Observations were weighted from 1 to 5, with 1 for reports from inexperienced observers to 5 for definitive and unambiguous TLP events.

The periodogram analysis comparing the frequency of TLPs with the sunspot cycle utilized a tool available from NASA’s Exoplanet Database to evaluate the data. If there was any mechanism whereby TLPs were being generated by solar activity, it had been suggested previously by Wilkins that perhaps out-gassing was being caused be solar irradiation or lunar dust was becoming electrostatically charged and suspended.

In fact, Surveyor 7 witnessed such a phenomenon during lunar twilight. To date, no human has witnessed a sunrise or sunset from the surface of the Moon, although astronauts witnessed several from lunar orbit.

"Horizon glow" as imaged from the lunar surface during twilight. (Credit: NASA).
“Horizon glow” as imaged from the lunar surface during twilight. (Credit: NASA).

The final conclusion of the BAA study cites that “Although there are theories that might infer that TLP would be more frequent during solar activity, from a sunspot cycle perspective there is no evidence to support this.”

The report provides an interesting perspective on the topic, especially with solar cycle 24 peaking over the next year. It also seems that reports of TLPs have declined in past decades. One of the most famous examples was the flash imaged on the Moon (thought to be a Leonid) by Leon Stuart in 1953. But in the modern era of astrophotography with the Moon under nearly continuous scrutiny, where are all the images of TLPs?

Granted, a core number (2%) of events suggest evidence of real activity on a Moon that we most often think of as geologically dead. As for the spurious sightings, it helps to recall the number of “sightings” in the 19th century of Vulcan transiting the face of the Sun. Where is Vulcan today, with the Sun being monitored around the clock?

We’re not immune to this sort of “echo effect” in the modern world of astronomy, either. For example, whenever an impact scar or flash is noted on Jupiter, as occurred in 2009 and 2012, other sightings are “seen” throughout the solar system. A similar psychological phenomenon occurred when Comet Holmes brightened in 2007. For a time, reports flying around the Internet suggested many comets where suddenly increasing in brightness!

It also interesting to note that many features such as Aristarchus and Ina Caldera also have a high brightness or albedo. Although the Full Moon seems pearly white, the albedo of the Moon is actually quite low at (13%), about that of worn asphalt. Bright ejecta and rays tend to stand out, especially approaching a Full Moon, such as occurs on May 25th.

You can even enhance the saturation of those lunar pics to bring out subtle color and reveal that the Moon isn’t as monochromatic as it appears to the naked eye;

A false-colored gibbous Moon enhanced to bright out subtle color. (Photo by author).
A false-colored gibbous Moon enhanced to bring out subtle color. (Photo by author).

Kudos to the team at the BAA for casting a critical scientific eye on a little studied phenomenon. Perhaps missions such as the Lunar Atmosphere and Dust Environment Explorer (LADEE) departing for the Moon this summer will shed more light on the curious nature of Transient Lunar Phenomena.

-The study can be read in the March 2013 edition of the British Astronomical Association’s Lunar Section Circular available as a free pdf.

Posted on by David Dickinson

The Return of Saturn: A Guide to the 2013 Opposition

A fine recent view of Saturn as captured by Daniel Robb. (Credit & Copyright: Daniel Robb/Universe Today flickr community. All rights reserved).

A star party favorite is about to return to evening skies.

The planet Saturn can now be spied low to the southeast for northern hemisphere observers (to the northeast for folks in the southern) rising about 1-2 hours after local sunset this early April. That gap will continue to close until Saturn is opposite to the Sun in the sky later this month and rises as the Sun sets.

Opposition occurs on April 28th at 8:00 UT/4:00AM EDT. Saturn will shine at magnitude +0.1 and appear 18.8” in diameter excluding the rings, which give it a total angular diameter of 43”.

Saturn has just passed into the faint constellation Libra for 2013, although its springtime retrograde loop will bring it back into Virgo briefly. Both the 2013 and 2014 opposition will occur in Libra. Saturn will also pass 26’ from +4.2 Kappa Virginis on July 3rd as it moves back into Virgo while in retrograde before resuming direct motion back into Libra.

Saturn currently lies about 15° to the lower left of the +1.04 magnitude star Spica, also known as Alpha Virginis. Remember the handy saying to “Spike to Spica” from the handle of the Big Dipper asterism to locate the region. Another handy finder tip; stars twinkle, planet generally don’t. That is, unless your skies are extremely turbulent!

With an orbital period 29.46 years, Saturn moves slowly eastward year to year, taking 2-3 years to cross through each constellation along the ecliptic.

Oppositions are roughly 378 days apart and thus move forward on our calendar by about two weeks a year. Successive oppositions also move about 13° eastward per year.

Saturn as imaged by the author on June 11th, 2012.
Saturn as imaged by the author on June 11th, 2012.

Oppositions of the ringed planet are also currently becoming successively favorable for southern observers over the coming years. Saturn crossed into the southern celestial hemisphere some years back, and will be at its southernmost in 2018.

Saturn won’t pass north of the celestial equator again until early 2026. Saturn is 15 million kilometres farther from us than opposition last year as its moving toward aphelion in 2018.

Saturn will reach eastern quadrature this summer on July 28th and stand its highest south at sunset northern hemisphere observers. South of the equator, it will pass directly overhead or transit to the north. Saturn will be with us for most of the remainder of 2013 in evening skies until reaching solar conjunction on November 6th.

Looking at Saturn with binoculars, you’ll immediately note that something is amiss.

You’re getting a view similar to that of Galileo, who sketched Saturn as a sort of “double handled cup.” In fact, it wasn’t until 1655 that Christian Huygens correctly hypothesized that the rings of Saturn are a flat disk that is not physically in contact with the planet.

Huygens also discovered the large moon Titan. Shining at magnitude +8.5 and taking 16 days to orbit Saturn, Titan is the second largest moon in our solar system after Ganymede. Titan would easily be a planet in its own right if it orbited the Sun. Titan is easily picked out observing Saturn at low power through a telescope.

Saturn's system of moons visible through a small telescope. orientation is for May 9th, 2013. (Created by the author using Starry Night).
Saturn’s system of moons visible through a small telescope. orientation is for May 9th, 2013. (Created by the author using Starry Night).

Observing Saturn at slightly higher magnification, five moons interior to Titan become apparent. From outside in, they are Rhea, Dione, Tethys, Enceladus, and Mimas. Exterior to Titan is the curious moon of Iapetus. Taking 79 days to complete one orbit of Saturn, Iapetus varies in brightness from magnitude +11.9 to +10.2, or a factor of over 5 times. Arthur C. Clarke placed the final monolith in the book adaptation of 2001: A Space Odyssey on Iapetus for this reason. Close-ups from the Cassini spacecraft reveal a two-faced world covered with a dark leading hemisphere and a bright trailing side, but alas, no alien artifacts.

But the centerpiece of observing Saturn through a telescope is its brilliant and complex system of rings. The A, B, and C rings are easily apparent through a backyard telescope, as is the large spacing known as the Cassini Gap.

The rings are also currently tilted in respect to our Earthly vantage point. The rings were edge-on in 2009 and vanish when this occurs every 15-16 years.

This year, we see the rings of Saturn at a respectable 19 ° opening and widening. The rings will appear at their widest at over 25° in 2017 and then become edge-on again in 2025.

The average tilt of Saturn's ring system as seen from Earth spanning 2008-2026. (Graph created by author).
The average tilt (in degrees) of Saturn’s ring system as seen from Earth spanning 2008-2026. (Graph created by author).

The ring system of Saturn adds 0.7 magnitudes of overall brightness to the planet at opposition this year.

Another interesting optical phenomenon to watch for in the days leading up to opposition is known as the “opposition surge” in brightness, or the Seeliger effect.  This is a retro-reflector effect familiar to many as high-beam headlights strike a highway sign. Think of the millions of particles making up Saturn’s rings as tiny little “retro-reflectors” focusing sunlight back directly along our line of sight. The opposition surge has been noted for other planets, but it’s most striking for Saturn when its rings are at their widest.

The disk of Saturn will cast a shadow straight back onto the rings around opposition and thus vanish from our view. The shadow across the back of the rings will then become more prominent over subsequent months, reaching its maximum angle at quadrature this northern hemisphere summer and then beginning to slowly slide back behind the planet again. A true challenge is to glimpse the disk of the through the Cassini gap in the rings… you’ll need clear steady skies and high magnification for this one!

It’s also interesting to note a very shallow partial lunar eclipse occurs with Saturn nearby just three days prior to opposition on April 25th. Saturn will appear 4° north of the Moon and it may be just possible to image both in the same frame.

The location of Saturn and the Full Moon during the April 25th partial eclipse. (Created by the author using Starry Night).
The location of Saturn and the Full Moon during the April 25th partial eclipse. (Created by the author using Starry Night).

Saturn takes about 30 years to make its way around the zodiac. I remember just beginning to observe Saturn will my new 60mm Jason refractor as a teenager in 1983 as it crossed the constellation Virgo.Hey, I’ve been into astronomy for over one “Saturnian year” now… where will the next 30 years find us?

Posted on by David Dickinson

A Look at the Hazards of Green Laser Pointers

An appropriate use of a laser during last year's Jupiter-Venus conjunction. (Photo by Author).

Those handheld green lasers pointers may not be as harmless as you thought.

A recent study released by researchers at the National Institute of Standards and Technology (NIST) has revealed an alarming trend. Of 122 hand-held laser pointers tested, 44% of red lasers and 90% of green lasers tested failed federal safety regulations.

The primary culprit was overpowered units. The Code of Federal Regulations in the United States limits commercial class IIIa lasers to 5 milliwatts (mW). And yes, lasers above 5 mW are commercially available in the United States, but it is illegal to market them as Class IIIa devices.  Some units in the NIST study  tested as high as 13 times over the legal limit at 66.5 mW. For context, many military grade rifle mounted lasers are rated at 50 mW.

A diagram of a typical diode-pumped solid-state laser. (Credit: NASA/Langley).
A diagram of a typical diode-pumped solid-state laser. (Credit: NASA/Langley).

“Our results raise numerous safety questions regarding laser pointers and their use,” stated NIST laser safety officer in the recent paper presented at the Laser Safety Conference in Orlando, Florida.

Why should backyard astronomers care? Well, since hand-held lasers first became commercially available they’ve become a familiar staple at many public star parties. Reflecting back off of the dust and suspended particles in the atmosphere, a green laser provides a pointer beam allowing the user to trace out constellations and faint objects. Lasers can also be mounted on the optical tube assemblies of a telescope for pointing in lieu of a finder scope.

A typical 5mW green laser pointer. (Photo by Author).
A typical 5mW green laser pointer. (Photo by Author).

An amateur astronomy club based near San Antonio, Texas even coordinated signaling the International Space Station with a pair of powerful searchlights and a 1 watt blue laser in 2012, just to prove that it was possible.

But such devices are not toys. Even a 5 mW laser can temporarily blind someone at short range. Further eye damage can often linger for days or even permanently and can go unnoticed. This is why researchers working around lasers in research facilities such as LIGO (the Laser Interferometer Gravitational Wave Observatory) must submit to routine eye exams.

Its not the Death Star... LIGO engineers practicing proper safety around the gravity wave observatory's 200 watt laser. Credit: NSF/LIGO).
Its not the Death Star… LIGO engineers practicing proper safety around the gravity wave observatory’s 35 watt Nd YAG laser. Credit: NSF/LIGO).

The trouble with green lasers is that, well, they look too much like light sabers.

It’s for this reason I keep mine on a very “short leash” at star parties and NEVER hand it off to anyone, no matter how well meaning, child or adult. I also NEVER point it below the local horizon, (there’s wildlife in them trees). A laser reflected inadvertently off of an optical surface such as a car window or primary mirror can also do just as much damage as a direct aiming.

And also, NEVER aim one at an aircraft. In fact, it’s a federal violation to do so. The Federal Aviation Administration has reported a 13-fold trend in reported aircraft/laser incidents from 2005 to 2011. There has also been an upward trend in individuals being tracked down and prosecuted for such offenses. If it blinks, assume it’s an aircraft and steer clear!

Reported incidents of laser/aircraft violations from 2005-2011. (Credit: Federal Aviation Administration).
Reported incidents of laser/aircraft violations from 2005-2011. (Credit: Federal Aviation Administration).

In a post-9/11 era, the Department of Homeland Security has been concerned with the potential threat posed by laser pointers as well. It’s not yet illegal to fly in the US with a 5mW laser pointer in your carry-on luggage, but and several countries now outlaw them all together, a note for traveling astronomers. Note that the de facto policy often comes down to the particular TSA officer you’re dealing with.

With this sort of news, we wonder if laser pointers might become outlawed entirely in the coming years. 5mW range lasers are generally classed IIIa or 3R systems. By the American National Standards Institute (ANSI) guidelines, such devices under the recent NIST study would fall into the much more hazardous IIIb range for 5-500 mW lasers. Such lasers can cause permanent eye damage with direct exposure for periods of as little as 1/100th of a second.

Safety distances for a 5mW green laser. (Wikimedia Commons graphic under a Creative Commons Attribution-ShareAlike 30 License).
Safety distances for a 5mW green laser. (Wikimedia Commons graphic under a Creative Commons Attribution-ShareAlike 3.0 License).

It’s also worth noting that actual reported cases of laser injuries are fairly rare. A 2004 paper from the Archives of Ophthalmology cites 15 injuries worldwide each year, while a recent 2012 paper in PLoS ONE estimates “220 confirmed laser eye injuries have occurred between 1964 and 1996,” for an average of 6.9 laser injuries per year.

The Code of Federal Regulations limits output for green laser pointers to 5mW in the visible range and 2mW in the infrared. 75% of the tested devices exceed this standard for infrared emission as well. Note that there have been anecdotal reports that even the point source generated by a laser (say, by shining it against a wall) can be excessively bright. This recent NIST study was the first time we’d seen a back up argument for this. Many of the cheaper handheld lasers sold online (think in the 20$ USD range) may forgo the infrared filtering component all together.

So in lieu of an outright ban on laser pointers, what can be done? Joshua Hadler cites the need for a better accountability for laser manufacturers. “By relying on manufacturers’ traceability to a national measurement institute such as NIST, someone could use this design to accurately measure power from a laser pointer.” Mr. Hadler also notes that a simple test bed for laser pointers can be built using off the shelf parts for less than $2,000 USD. We’re surprised there’s not “an App/Kickstarter for that…” already. (Would-be designers take note!)

In the end, we’d hate to see these crucial tools for astronomy outreach  banned just because a very few individuals were irresponsible with them. Through accountability from production to application, we can assure that laser pointers remain a vital part of the amateur astronomer’s tool kit.

Posted on by David Dickinson

Comet Lemmon: A Preview Guide for April

Comet C/2012 F6 Lemmon as imaged by Luis Argerich as from near Buenos Aires, Argentina on March (Credit: Nightscape photography. Used with permission).

As Comet 2011 L4 PanSTARRS moves out of the inner solar system, we’ve got another comet coming into view this month for northern hemisphere observers. 

Comet C/2012 F6 Lemmon is set to become a binocular object low to the southeast at dawn for low northern latitudes in the first week of April. And no, this isn’t an April Fools’ Day hoax, despite the comet’s name. Comet Lemmon (with two m’s) was discovered by the Mount Lemmon Sky Survey (MLSS) based outside of Tucson, Arizona on March 23, 2012. MLSS is part of the Catalina Sky Survey which searches for Near Earth Asteroids. We’ve got another comet coming into view this month for northern hemisphere observers as Comet 2011 L4 PanSTARRS moves out of the inner solar system.

The comet is on an extremely long elliptical orbit, with a period of over 11,000 years. Comet Lemmon just passed perihelion at 0.74 astronomical units from the Sun on March 24th.

Animation of Comet Lemmon as it passes the star Gamma Crucis on January 17th. (Courtesy of Luis Argerich. Used with permission).
Animation of Comet Lemmon as it passes the star Gamma Crucis on January 17th. (Courtesy of Luis Argerich. Used with permission).

Southern hemisphere observers have been getting some great views of Comet Lemmon since the beginning of this year. It passed only three degrees from the south celestial pole on February 5th, and since that time has been racing up the “0 Hour” line in right ascension. If that location sounds familiar, that’s because another notable comet, 2011 L4 PanSTARRS has been doing the same. In fact, astrophotographers in the southern hemisphere were able to catch both comets in the same field of view last month.

Another celestial body occupies 0 Hour neighborhood this time of year. The Sun just passed the vernal equinox marking the start of Spring in the northern hemisphere and Fall in the southern on March 19th.

And like PanSTARRS, Comet Lemmon has a very steep orbit inclined 82.6° relative to the ecliptic.

The steep path and current position of Comet Lemmon. (Credit: NASA/JPL' Small-Body Database Browser).
The steep path and current position of Comet Lemmon. (Credit: NASA/JPL’ Small-Body Database Browser).

Comet Lemmon broke naked-eye visibility reaching +6th magnitude in late February and has thus far closely matched expectations. Current reports place it at magnitude +4 to +5 as it crosses northward through the constellation Cetus. Predictions place the maximum post-perihelion brightness between magnitudes +3 and +5 in early April, and thus far, Comet Lemmon seems to be performing right down the middle of this range.

Brightness graph for Comet Lemmon for the months surrounding perihelion. (Created by author).
Brightness graph for Comet Lemmon for the months surrounding perihelion. (Created by author).

Southern observers have caught a diffuse greenish 30” in diameter nucleus on time exposures accompanied by a short, spikey tail. Keep in mind, the quoted brightness of a comet is extended over its entire surface area. Thus, while a +4th magnitude star may be easily visible in the dawn, a 3rd or even 2nd magnitude comet may be invisible to the unaided eye. Anyone who attempted to spot Comet PanSTARRS in the dusk last month knows how notoriously fickle it actually was. Binoculars are your friend in this endeavor. Begin slowly sweeping the southeast horizon about an hour before local sunrise looking for a fuzzy “star” that refuses to reach focus. Comet Lemmon will get progressively easier in the dawn sky for latitudes successively farther north as the month of April progresses.

The apparent path of Comet Lemmon for April looking southeast about an hour before local sunrise from latitude 30 degrees north. (Created by the Author using Starry Night).
The apparent path of Comet Lemmon for April 10th through the 30th looking east about an hour before local sunrise from latitude 30 degrees north. (Created by the Author using Starry Night).

Comet Lemmon will continue to gain elevation as it crosses from Cetus into the constellation Pisces on April 13th. An interesting grouping occurs as the planet Mercury passes only a few degrees from the comet from April 15th to April 17th. Having just past greatest elongation on March 31st, Mercury will shine at magnitude -0.1 and make a good guide to locate the comet in brightening dawn skies. The pair is joined by the waning crescent Moon on the mornings of April 7th and 8th which may also provide for the first sighting opportunities from low north latitudes around these dates.

The apparent path of Comet Lemmon for April looking southeast about an hour before local sunrise from latitude 30 degrees north. (Created by the Author using Starry Night).
Mercury meets Comet Lemmon on April 15th as seen about an hour before local sunrise from latitude 30 degrees north. (Created by the Author using Starry Night).

The Moon reaches New phase on Wednesday, April 10th at 5:35AM EDT/9:35 UT. It will be out of the morning sky for the next couple of weeks until it reaches Full on April 25th, at which point it will undergo the first eclipse of 2013, a very shallow partial. (More on that later this month!)

Comet Lemmon will then slide across the celestial equator on April 20th and cross the plane of the ecliptic on April 22nd as it heads up into the constellation Andromeda in mid-May. We’re expecting Comet Lemmon to be a fine binocular object for late April, but perhaps not as widely observed due to its morning position as PanSTARRS was in the dusk.

By mid-May, Comet Lemmon will have dipped back down below +6th magnitude and faded out of interest to all but a few deep sky enthusiasts. Comet Lemmon will pass within 10° of the north celestial pole on August 9th, headed back out into the icy depths of the solar system not to return for another 11,000-odd years.

It’s interesting to see how these two springtime comets will effect observers expectations for the passage of Comet C/2012 S1 ISON. Will this in fact be the touted “Comet of the Century?” Much hinges on whether ISON survives its November 28th perihelion only 1,166,000 kilometers from the center of our Sun (that’s 0.68 solar-radii or about 3 times the Earth-Moon distance from the surface of the Sun). If so, we could be in for a fine “Christmas Comet” rivaling the passage of Comet Lovejoy in late 2011. On the other hand, a disintegration of Comet ISON would be more akin to the fizzle of Comet Elenin earlier in 2011.

In the meantime, enjoy Comet Lemmon as an Act 2 in the 2013 Three Act “Year of the Comet!”

Posted on by David Dickinson

See Mercury at its Greatest Elongation for 2013

Mercury gives a clue to Super-Mercuries
Astronomers have found a star system with two planets like Mercury, but bigger. Our own Mercury could supply clues to their composition and formation. (Credit: NASA/Johns Hopkins University/Applied Physics Laboratory.Carnegie Institution of Washington).

A fine apparition of the planet Mercury graces the dawn skies this week, leading up to its greatest elongation from the Sun for 2013.

It seems that nearly every appearance of the planet Mercury is touted as the “best” these days. Such was the case with the inner-most world’s dusk showing early last month. Truth is, all elongations of Mercury (and Venus, for that matter) are not created equal, and visibility of each apparition isn’t the same for observers worldwide. We’ll show you why.

Mercury orbits the Sun once every 88 days. With an orbit interior to our own, it never strays far from the Sun in the sky and thus can only appear low in the dawn or dusk. Its orbit is also elliptical, with an eccentricity of 0.206, the greatest of any planet in our solar system. This means that greatest elongations can vary considerably, from 17.9° away from the Sun in the sky near perihelion of the planet to 28.7° near aphelion. And although reaching greatest elongation near aphelion means the tiny world is above the muck of the horizon, it also means it’s also intrinsically a bit fainter; Mercury can vary in brightness from magnitude -0.2 at a perihelic-elongation to half a magnitude fainter at +0.3 for an aphelic-elongation.

A comparison of elongations of Mercury as seen from the Earth at perihelion versus aphelion. (Created by the author).
A comparison of elongations of Mercury as seen from the Earth at perihelion versus aphelion. (Created by the author).

But there’s more. Compounding this situation is the angle of the ecliptic, or the imaginary plane of the orbit of the Earth. Near the March equinox the ecliptic rides high in the dusk to the west and low in the dawn to the east for northern hemisphere observers. In the southern hemisphere, the reverse is true. It’s a strange sight for a northerner to head “Down Under” and watch the Sun rise in the east, transit to the north and set to the west!

The path of Mercury looking east ~45 minutes prior to sunrise from latitude 30 degrees north from March 26th through April 30th, (Created by the author using Starry Night).
The path of Mercury looking east ~45 minutes prior to sunrise from latitude 30 degrees north from March 26th through April 30th, (Created by the author using Starry Night).

Thus what may be a terrible apparition of Mercury for one hemisphere may be a grand one for another, as is the case this week. Yes, northern observers can catch the fleeting world, if they know exactly where to look for it. For observers based at longitude 40° north, Mercury will never peak above an altitude of 10° in the dawn sky. Observers based near 35° south will however see the planet reach its maximum possible elevation of over 25° degrees above the horizon.

We would qualify this as “The best dawn appearance of Mercury for 2013… as seen from the southern hemisphere.” Greatest elongations of Mercury occur in pairs, with dusk-to-dawn apparitions about 45 days apart as the planet passes between us and the Sun, followed by a longer period of about 70 days as the world loops back around behind the Sun. The orbit of Mercury is tilted about 7° with respect to our own. Otherwise, we would see a transit of the planet every inferior conjunction, as last occurred on November 8th, 2006 and will happen next on May 9th, 2016.

The path of Mercury from March 26th through April 26th looking east from latitude 35 degrees south ~45 minutes prior to sunrise. (Created by the author using Starry Night).
The path of Mercury from March 26th through April 26th looking east from latitude 35 degrees south ~45 minutes prior to sunrise. (Created by the author using Starry Night).

Mercury will show a maximum illumination area of 38.5” square arc seconds as seen from the Earth March 30th on just before reaching its greatest elongation west of the Sun on March 31st on Easter Day at 22:00 UT/18:00EDT. Through a telescope, Mercury will display a 7.7” diameter disk with a 50% illuminated “half-Moon” phase. Mercury reaches greatest elongation just 28 hours prior to aphelion which occurs on April 2nd, the closest this has occurred date-wise since April 8th, 2006. This won’t be matched again until March 24th, 2020. Shining at magnitude +0.3, Mercury will then race ahead of the Earth on its inside track and will begin to gradually sink lower on successive mornings in early April. The morning of April 8th may well offer the last good chance to spy the tiny world when the old crescent Moon passes just 8° degrees north of the planet within two days of reaching New phase on April 10th. Mercury reaches superior conjunction opposite to the Earth and on the far side of the Sun on May 11th, 2013, and will again head into the dusk skies for its next greatest eastern elongation on June 12th.

From our Earthly vantage point, Mercury completes 3.15 orbits of the Sun a year. This means that we see 6 greatest elongations on average most years, 3 westerns (dawn) and 3 easterns (dusk). The most elongations of Mercury that you can have in a calendar year are 7, which occurred in 2011 and will happen again in 2015. It’s fascinating to think that until the advent of the Space Age, the orbit and the rough size of Mercury was all we knew about the planet. It would take the first flyby of the Mariner 10 spacecraft to give us a close up view of Mercury in 1974. The precession of the orbit of Mercury was a mystery until explained by Einsteinian physics, and still stands as one of the great proofs of general relativity. Today, we have a permanent ambassador around Mercury, NASA’s MESSENGER spacecraft. MESSENGER has mapped to world in detail, sampled its tenuous exosphere, and observed hints of ancient volcanic activity. MESSENGER will be followed by the joint European Space Agency/Japan Aerospace Exploration Agency mission BepiColombo set to launch in 2015 which will arrive at Mercury in 2022. All fascinating things to ponder as you search for the diminutive world low in the dawn skies this coming Easter weekend!

Posted on by David Dickinson

Stalking the Lunar X

The Lunar X, captured by the author on June 8th, 2011.

This week offers observers a shot at capturing a fascinating but elusive lunar feature.

But why study the Moon? It’s a question we occasionally receive as a backyard astronomer. There’s a sort of “been there, done that” mentality associated with our nearest natural neighbor in space. Keeping one face perpetually turned Earthward, the Moon goes through its 29.5 synodic period of phases looking roughly the same from one lunation to the next. Then there’s the issue of light pollution. Many deep sky imagers “pack it in” during the weeks surrounding the Full Moon, carefully stacking and processing images of wispy nebulae and dreaming of darker times ahead…

But fans of the Moon know better. Just think of life without the Moon. No eclipses. No nearby object in space to give greats such as Sir Isaac Newton insight into celestial mechanics 101. In fact, there’s a fair amount of evidence to suggest that life arose here in part because of our large Moon. The Moon stabilizes our rotational axis and produces a large tidal force on our planet. And as all students of lunar astronomy know, not all lunations are exactly equal.

A daytime capture of the Lunar X. (Photo by Author).
A daytime capture of the Lunar X. (Photo by Author).

This week, we get a unique look at a feature embedded in the lunar highlands which demonstrates this fact. The Lunar X, also sometimes known as the Purbach cross or the Werner X reaches a decent apparition on March 19th at 11:40UT/7:40EDT favoring East Asia and Australia. This feature is actually the overlapping convergence of the rims of Blanchinus, La Caille and Purbach craters. The X-shaped feature reaches a favorable illumination about six hours before 1st Quarter phase and six hours after Last Quarter phase. It is pure magic watching the X catch the first rays of sunlight while the floor of the craters are still immersed in darkness. For about the span of an hour, the silver-white X will appear to float just beyond the lunar terminator.

Visibility of the Lunar X for the Remainder of 2013.
Lunation Date Time Phase Favors
1116 March 19th 11:40UT/7:40EDT Waxing East Asia/Australia
1116 April 3rd 3:20UT/23:20EDT* Waning Africa/Europe
1117 April 17th 23:47UT/19:47EDT Waxing Eastern North America
1117 May 2nd 16:19UT/12:19EDT Waning Central Pacific
1118 May 17th 10:51UT/6:51EDT Waxing East Asia/Australia
1118 June 1st 4:31UT/0:31EDT Waning Western Africa
1119 June 15th 21:21UT/17:21EDT Waxing South America
1119 June 30th 16:04UT/12:04EDT Waning Western Pacific
1120 July 15th 7:49UT/3:49EDT Waxing Australia
1120 July 30th 3:16UT/23:16EDT* Waning Africa/Western Europe
1121 August 13th 18:50UT/14:50EDT Waxing South Atlantic
1121 August 28th 14:27UT/10:27EDT Waning Central Pacific
1122 September 12th 9:50UT/5:50EDT Waxing East Asia/Australia
1122 September 27th 2:00UT/22:00EDT* Waning Middle East/East Africa
1123 October 11th 19:52UT/15:52EDT Waxing Atlantic Ocean
1123 October 26th 14:12UT/10:12EDT Waning Central Pacific
1124 November 10th 10:03UT/5:03EST Waxing East Asia/Australia
1124 November 25th 3:14UT/22:14EST* Waning Africa/Europe
1125 December 10th 00:57UT/19:57EST Waxing Western North America
1126 December 24th 17:07UT/12:07EST Waning Western Pacific
*Times marked in bold denote visibility in EDT/EST the evening prior.

 

Fun Factoid: All lunar apogees and perigees are not created equal either. The Moon also reaches another notable point tonight at 11:13PM EDT/ 3:13 UT as it arrives at its closest apogee (think “nearest far point”) in its elliptical orbit for 2013 at 404,261 kilometres distant. Lunar apogee varies from 404,000 to 406,700 kilometres, and the angular diameter of the Moon appears 29.3’ near apogee versus 34.1’ near perigee. The farthest and visually smallest Full Moon of 2013 occurs on December 17th.

The first sighting of the Lunar X feature remains a mystery, although modern descriptions of the curious feature date back to an observation made by Bill Busler in June 1974. As the Sun rises across the lunar highlands the feature loses contrast. By the time the Moon reaches Full, evidence of the Lunar X vanishes all together. With such a narrow window to catch the feature, many longitudes tend to miss out during successive lunations. Note that it is possible to catch the 1st and Last Quarter Moon in the daytime.

A 1st Quarter Moon with the Lunar X (inset). (Photo by Author).
A 1st Quarter Moon with the Lunar X (inset). (Photo by Author).

Compounding the dilemma is the fact that the lighting angle for each lunation isn’t precisely the same. This is primarily because of two rocking motions of the Moon known as libration and nutation. Due to these effects, we actually see 59% of the lunar surface. We had to wait for the advent of the Space Age and the flight of the Soviet spacecraft Luna 3 in 1959 to pass the Moon and look back and image its far side for the first time.

We actually managed to grab the Lunar X during a recent Virtual Star Party this past February. Note that another fine example of lunar pareidolia lies along the terminator roughly at the same time as the Lunar X approaches favorable illumination. The Lunar V sits near the center of the lunar disk near 1st and Last Quarter as well and is visible right around the same time. Formed by the confluence of two distinct ridges situated between the Mare Vaporum and Sinus Medii, it is possible to image both the Lunar X and the Lunar V simultaneously!

A simultaneous capture of the Lunar X & the Lunar V features. (Photo by Author).
A simultaneous capture of the Lunar X & the Lunar V features. (Photo by Author).

This also brings up the interesting possibility of more “Lunar letters” awaiting discovery by keen-eyed amateur observers… could a visual “Lunar alphabet be constructed similar to the one built by Galaxy Zoo using galactic structures? Obviously, the Moon has no shortage of “O’s,” but perhaps “R” and “Q” would be a bit more problematic. Let us know what you see!

-Thanks to Ed Kotapish for providing us with the calculations for the visibility of the Lunar X for 2013.

 

Posted on by David Dickinson

Citizen Science, Old-School Style: The True Tale of Operation Moonwatch

An Operation Moonwatch team in action based out of Terre Haute, Indiana. (Courtesy of Keep Watching the Skies! Author Patrick McCray, used with Permission).

Amateur astronomers have done more than just watch the skies, they’ve been a national security asset. In the mid-1950’s, it was realized that the reality of the Space Age was at best only a decade away. Sub-orbital German V-2 rockets captured by the Soviets and the United States were reaching higher and higher altitudes, and it was only a matter of time before orbital velocity would be achieved.

Keep in mind, this was the age of backyard bomb shelters, “duck and cover” drills, and civil preparedness as Cold War fever reached a heightened pitch. Ground Observer Corps encouraged and trained citizen groups how to spot and report enemy bombers approaching the U.S coast in preparation for a nuclear confrontation. And remember, there was no reason to think that this build up wouldn’t extend to the militarization of space. It was in this era that Operation Moonwatch was born.

Conceived by Harvard astronomer Fred Whipple, Operation Moonwatch was the “Galaxy Zoo” of its day. The idea was simple; teams of observers around the world would track, time and record satellite passes over their location and feed this data back to the computation center at Cambridge, Massachusetts (telephone, Western Union or ham radio were the methods of the day) This data would give engineers information as to where to point their enormous Baker-Nunn cameras. These instruments were wide-field Schmidt cameras that could cover large swaths of the sky. They were to be positioned at 12 locations worldwide to keep tabs on satellites in low Earth orbit (LEO).

A Baker-Nunn satellite tracking camera ready for action. (Credit: NASA).
A Baker-Nunn satellite tracking camera ready for action. (Credit: NASA).

To be sure, there were obstacles to overcome. The Baker-Nunn cameras were well behind schedule, and the entire system was struggling to come online by mid-1958 in time for the International Geophysical Year (IGY). School and community groups had to be organized, trained, and equipped. Knowing precise location in the pre-GPS era had to be addressed. Many purchased optical kits available from Radio Shack, while many teams built their own. Then there was the dilemma of what a satellite would actually look like to an observer on the ground. Could a trained spotter even see it? Civil Air Patrol groups experimented with various trial substitutions, such as following aircraft, flocks of birds and bats at dusk and even tracking pebbles tossed into the sky!

Operation Moonwatch was also to play a part of the 1958 International Geophysical Year. Many doubted to effectiveness of amateur groups, but public interest ran high. Then on October 4th 1957, the world was caught off guard as Sputnik 1 lifted off from the Baikonur Cosmodrome.

The metal ball that started it all... Sputnik 1. (Credit: NASA/Asif A. Siddiqi).
The metal ball that started it all… Sputnik 1. (Credit: NASA/Asif A. Siddiqi).

The world was stunned that the Soviets had beaten the West into space. The National Advisory Committee for Aeronautics (later to become NASA in 1958) had yet to achieve a successful orbital launch, and the United States Naval Research Laboratory was still floundering to get the Vanguard program off the pad. The launch of Sputnik found a scant few Moonwatch teams at the ready to catch its first dusk passes over the United States. Keep in mind, the Sputnik satellite was too small and faint to see with the naked eye. What most casual observers in the general public saw (remember the opening scenes in the movie October Sky?) was actually the rocket booster that put Sputnik into space.

Moonwatch teams would “look up by looking down” using a bench mounted telescope that looked at a reflective plate aimed skyward. With observers arranged in a row aimed at a picket line, they would call out when the target satellite crossed the local meridian. This would in turn be documented by an onsite recorder for transmission.

A classic Operation Moonwatch bench instrument sold by Edmund Scientifc. (Credit: The Smithsonian Natinal Air & Space Museum).
A classic Operation Moonwatch bench instrument sold by Edmund Scientific  (Credit: The Smithsonian National Air & Space Museum).

With Sputnik, the Operation Moonwatch volunteers found themselves thrust into the spotlight. Newspapers & radio shows clamored to interview volunteers, as the public suddenly became obsessed with space. Moonwatchers followed and documented to launch of the dog Laika aboard Sputnik 2 on November 3rd, 1957, and when the U.S. finally launched its first satellite Explorer I on February 1st 1958 Operation Moonwatch tracked it. Magazines such as National Geographic and Boys Life ran articles on the project and told teams how they could participate. When Sputnik 4 reentered over the U.S. on September 1962, it was data from Operation Moonwatch observers that proved vital in its recovery.

How Operation Moonwatch fit into the hierarchy. (Credit: NASA archives, The Role of the NAS & TPESP).
How Operation Moonwatch fit into the hierarchy. Note how amateur groups were associated with this press. (Credit: NASA archives, The Role of the NAS & TPESP).

Moonwatch was disbanded in 1975, but many volunteers continued tracking satellites and sharing data on their own. I always think that it’s fascinating that three very early satellites from the early days of Operation Moonwatch are still in orbit and can been seen with a good pair of binoculars and a little patience , Vanguards 1, 2 & 3. It could be argued that Operation Moonwatch provided a civilian means to monitor the goings on of governments in low Earth orbit and may have contributed to the Outer Space Treaty outlawing the use of nuclear weapons in space. Another fortunate occurrence of the era was the establishment of a civilian space agency in the U.S., argued for successfully by Dr. James Van Allen. How different would the course of history have been if the U.S. space program had become a “fourth branch” of the military?

Cincinnati plaque commemorating Operation Moonwatch. (Brian Van Flandern Public Domain image).
Cincinnati plaque commemorating Operation Moonwatch. (Brian Van Flandern Public Domain image).

Today, modern satellite trackers still follow, image and share information on satellites worldwide. This effort transcends borders; when hazardous payloads such as Russia’s failed Mars mission Phobos-Grunt reentered in early 2012 satellite trackers documented its final passage, and efforts are still underway to keep tabs on the USAF’s X-37 spy satellite. One can also see a stark contrast between the efforts to enlist civilian effort during the Cold War and the modern Global War on Terrorism. Interest in science was at an all-time high in the 1950’s, as it was realized the West might be lagging behind in science education. In a post-9/11 era, there almost seems to be a movement to isolate participation. Many model rocketry groups are under increased restriction, and even amateur astronomers may see essential tools such as green laser pointers restricted for use.

Image of Space Shuttle Discovery on STS-119 captured from the ground... note the NASA "Blue Meatball" logo on the wing! (Credit Ralf Vandebergh, used with permission).
Image of Space Shuttle Discovery on STS-119 captured from the ground… note the NASA “Blue Meatball” logo on the wing! (Credit:  Ralf Vandebergh, used with permission).

But the good news is, anyone can still track a satellite from the comfort of their own backyard all in the spirit of Operation Moonwatch. DARPA announced a project last year which may resurrect a program similar to Operation Moonwatch. Named SpaceView, this program seeks to augment the U.S. Air Force’s Space Surveillance Network. Keep an eye on the sky, and remember a dedicated few amateur observers that played a crucial role in modern history as you watch satellites drift silently by in the twilight skies.

For more on the fscinating hostory of Operation Moonwatch, read Patrick McCray’s Keep Watching the Skies!

See more of Ralf Vandebergh’s outstanding work at his site Telescopic Spaceflight Images.

Posted on by David Dickinson

12 Star Party Secret Weapons

Awaiting sunset... (Photo by author).

We’ve all been there. Well OK, all public star party telescope operators have been there. You’re set up and you’ve got a stunning view of Saturn centered in the field of view. But then the first member of the viewing public takes a quick glance and steps back from the eyepiece, stating “yeah, I saw that through the last four ‘scopes…”

What do you do when every telescope down the row is aimed at the same object? Or worse yet, what do you aim at when there is no Moon or bright planets above the horizon? Every seasoned telescope operator has a quick repertoire of secret favorites, little known but sure-fire crowd pleasers.  Sure, Saturn is awesome and you should see it through a telescope… but it’s a big universe out there. 

I’ve even seen clubs assign objects to individual telescopes to avoid having everyone point at the same thing, but this method is, well, boring for the scope operators themselves.  Most backyard astronomers can simply look at a tube pointed at Orion and know the neighboring telescope is aimed at the Orion Nebula. What follows is our very own highly subjective (but tested in the field!) list of secret star party faves. Yes, it is mid-northern latitude-centric. It also covers a span of objects of all types, as well as a handy information chart of where in the sky to find ‘em and a few surprises. We also realize that many public star parties often take place downtown under light polluted skies, so a majority of these are brighter objects.  Don’t see your favorite? Drop us a line and let us know!

12. The Double Cluster:  Straddling the border of the constellations Perseus and Cassiopeia, this pair of clusters is a fine sight at low power. The technical designation of the pair is NGC 884 and NGC 869 respectively and the clusters sit about 7000 light years distant.  You can just see the pair with the naked eye under suburban skies.

The location of Herschel 3945 in Canis Major. (Created by Author in Starry Night).
The location of Herschel 3945 in Canis Major. (Created by Author in Starry Night).

11. Herschel 3945:  A popular summer-to-fall star party target is the colored double star Albireo is the constellation Cygnus. But did you know there’s a similar target visible early in the year as well? I call Herschel 3945 the “winter Albireo” for just this reason. This 27” split pair of sapphire and orange stars offers a great contrast sure to bring out the “ohs” and “ahs.” Continue reading “12 Star Party Secret Weapons”

Posted on by David Dickinson

Why This Weekend is Perfect for a Messier Marathon

To 'scopes, get set, marathon! (A homemade 14" Gregorian reflector, photo by author).

This coming weekend presents the first window for 2013 to complete a challenge in the realm of backyard astronomy and visual athletics. With some careful planning, persistence, and just plain luck, you can join the vaunted ranks of those seasoned observers who’ve seen all 110 objects in the Messier catalog… in one night.

Observing all of the objects in Messier’s catalog in a single night has become a bit of a sport over the last few decades for northern hemisphere observers, and several clubs and organizations now offer certificates for the same.  The catalog itself was a first attempt by French astronomer Charles Messier to catalog the menagerie of “faint fuzzies” strewn about the northern hemisphere sky.

Not that Charles knew much about the nature of what he was seeing. The modern Messier catalog includes a grab bag collection of galaxies, nebulae, open and globular clusters and more down to magnitude +11.5, all above declination -35°. Charles carried out his observations from Paris France at latitude +49° north. Unfortunately, this  also means that Messier catalog is the product of Charles Messier’s northern-based vantage point. The northernmost objects in the catalog are Messiers 81 & 82 at declination +69°, which never get above the horizon for observers south of latitude -21°. His initial publication of the catalog in 1774 contained 45 objects, and his final publication contained 103, with more objects added based on his notes after his death in 1817. (Fun fact: Messier is buried in the famous Père Lachaise Cemetery in Paris, site of other notable graves such as those of Chopin and Jim Morrison).

M51, the Whirlpool Galaxy, one of the more photogenic objects in the Messier catalog. (Credit: NASA/Hubble Heritage Project).
M51, the Whirlpool Galaxy, one of the more photogenic objects in the Messier catalog. (Credit: NASA/Hubble Heritage Project).

There’s a fair amount of controversy on Messier’s motivations and methods for compiling his catalog. The standard mantra that will probably always be with us is that Messier was frustrated with stumbling across these objects in his hunt for comets and decided to catalog them once and for all. He eventually discovered 13 comets in his lifetime, including Comet Lexell which passed only 2.2 million kilometres from Earth in 1770.

No one is certain where the modern tradition of the Messier Marathon arose, though it most likely had its roots in the amateur astronomy boom of the 1970s and was a fixture of many astronomy clubs by the 1980s. There are no Messier objects located between right ascension 21 hours 40 minutes  and 23 hours 20 minutes, and only one (M52)  between 23 hours 20 minutes and 0 hours 40 minutes. With the Sun reaching the “0 hour” equinoctial point on the March Vernal Equinox (falling on March 20th as reckoned in Universal Time for the next decade), all of the Messier objects are theoretically observable in one night around early March to early April. Taking into account for the New Moon nearest to the March equinox, the best dates for a weekend Messier marathon for the remainder of the decade are as follows;

Optimal Messier marathon dates for the remainder of the decade. (Compiled by author).
Optimal Messier marathon dates for the remainder of the decade. (Compiled by author).

Note that this year’s weekend is very nearly the earliest that it can occur. The optimal latitude for Messier marathoning is usually quoted as 25° north, about the latitude of Miami. It’s worth noting that 2013 is one of the very few years where the primary weekend falls on or before our shift one hour forward to Daylight Saving time, occurring this year on March 10th for North America.

Students of the Messier catalog will also know of the several controversies that exist within the list. For example, one wide double star in Ursa Major made its way into the catalog as Messier 40. There’s also been debate over the years as to the true identity of Messier 102, and most marathoners accept the galaxy NGC 5866 in its stead. Optics of the day weren’t the most stellar (bad pun intended) and this is evident in the inclusion of some objects but the omission of others. For example, it’s hard to imagine a would-be comet hunter mistaking the Pleiades (M45) for an icy interloper, but curiously, Messier omits the brilliant Double Cluster in Perseus.

M42, the Orion Nebula. (Photo by Author, taken back in the days of ye ole film!)
M42, the Orion Nebula. (Photo by Author, taken back in the days of ye ole film!)

It’s vital for Messier marathoners to run through objects in proper sequence. Most visual observers run these in groups, although Alex McConahay suggests in a recent April 2013 Sky & Telescope article that folks running a photographic marathon (see below) beware of wasting precious time crossing the celestial meridian (a maneuver which requires a telescope equipped with a German Equatorial mount to “flip” sides) hunting down objects. The unspoken “code of the skies” for visual Messier marathoners is that “Go-To” equipped scopes are forbidden. Part of the intended purpose of the exercise is to acquaint you with the night sky via star hopping to the target.

Most observers complete Messier objects in groups. You’ll want to nab M77 and M74 immediately after local dusk, or the marathon will be over before it starts. You’ll then want to move over to the Andromeda Galaxy and the collection of objects in its vicinity before scouring Orion and environs. From that point out, you can begin to slow down a bit and pace yourself through the galaxy groups in Coma Berenices and the Bowl of Virgo asterism. Another cluster of objects stretch out in the sky past midnight along the plane of our Milky Way Galaxy from Sagittarius to Cygnus, and the final (and often most troublesome) targets to bag are the Messier objects in Aquarius and M30 in Capricornus just before dawn. Remember, dark skies, warm clothes, and hot coffee are your friends in this endeavor!

There have been alternate rules or versions of Messier marathons over the years. Some imagers complete one-night photographic messier marathons. There are even abbreviated or expanded versions of the feat. It is also possible to nab most of the Messier catalog with a good pair of binoculars under clear skies. Probably the most challenging version we’ve heard of is sketching all 110 Messier objects in one evening… you might be forgiven for using a Go-To enabled telescope to accomplish this!

Finally, just like running marathons, the question we often get is why. Some may eschew transforming the art of dark sky observing into a task of visual gymnastics. We feel that to run through this most famous of catalogs in an evening is a great way to learn the sky and practice the fast-disappearing art of star hopping. And hey, no one’s saying you can’t take a year or three to finish the Messier catalog… its a big universe, and the New General Catalog (NGC) and Index Catalog (IC) containing thousands of objects will still be waiting. Have YOU seen all 110?

–      A perpetual listing of Messier marathon visibility by latitude by Tom Polakis.

–      An All Sky Map of the Messier catalog.

–      A handy priority list for a Messier marathon compiled by Don Machholz.

Posted on by David Dickinson

Spotting the Dragon: How to See SpaceX on Approach to the ISS This Weekend

Capture of the Dragon during the October 2012 CRS-1 mission. (Credit: NASA/ISS).

SpaceX’s Dragon spacecraft may be appearing in a backyard sky near you this weekend. Scheduled to launch this Friday on March 1st at 10:10 AM Eastern Standard Time (EST)/15:10 Universal Time (UT), this will be the 3rd resupply flight for the Dragon spacecraft to the International Space Station (ISS).  And the great news is, you may just be able to catch the spacecraft as it chases down the ISS worldwide.

The Space Shuttle and the ISS captured by the author as seen from Northern Maine shortly after undocking in June, 2007. 

Catching a satellite in low Earth orbit is an unforgettable sight. Satellites appear as moving “stars” against the background sky, shining steadily (unless they’re tumbling!) in the sunlight overhead in the dawn or dusk sky. Occasionally, you may catch a flare in brightness as a reflective panel catches the sunlight just right. The Hubble Space Telescope and the Iridium constellation of satellites can flare in this fashion.

At 109 metres in size, the ISS is the largest object ever constructed in orbit and is easily visible to the naked eye. It has an angular diameter of about 50” when directly overhead (about the visual size of Saturn plus rings near opposition). I can just make out a tiny box-like structure with binoculars when it passes overhead. If the orientation of the station and its solar panels is just right, it looks like a tiny luminous Star Wars TIE fighter as viewed through binoculars!

Dragon in the processing hangar at Cape Canaveral. (Credit: NASA/Kim Shiflett).
Dragon in the processing hangar at Cape Canaveral. (Credit: NASA/Kim Shiflett).

But what’s even more amazing is to watch a spacecraft rendezvous with the ISS, as diligent observers may witness this weekend. Your best bet will be to use predictions for ISS passes from your location. Heavens-Above, CALSky and Space Weather all have simple trackers for sky watchers. More advanced observers may want to use an application known as Orbitron which allows you to manually load updated Two-Line Element sets (TLEs) from Celestrak or NORAD’s Space-Track website for use in the field sans Internet connection. Note that Space-Track requires permission to access; they welcome amateur sat-spotters and educators, but they also want to assure that no “rogue entities” are accessing the site! Continue reading “Spotting the Dragon: How to See SpaceX on Approach to the ISS This Weekend”