Observing Archives

April 4, 2013December 23, 2015 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).

“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).

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).

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 1/100^th 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.

April 3, 2013December 23, 2015 by Nancy Atkinson

Incredible Views: Comet PANSTARRS Meets the Andromeda Galaxy

Two objects 2.5 million lightyears apart... PanSTARRS & Andromeda. Credit and copyright: Brendan Alexander.

We warned you it was going to happen, and here’s visual proof! In this comet encounter of the extragalactic kind, Comet PanSTARRS and the Andromeda Galaxy met each other in the skies above Earth. This great image by Brendan Alexander in Ireland shows the spectacular view. He said it was “a difficult image to capture due to low cloud, the low altitude of the target and tracking issue. I hope to get the chance to improve on this!”

Here’s another image from UT reader Anna Morris:

Comet PANSTARRS and the Andromeda galaxy over Suffolk, England on April 2, 2013. This composite images shows the movement of the comet during the imaging session. Credit and copyright: Anna Morris.

Want to see this meetup for yourself? Tonight might be even better:

Comet PANSTARRS shown every three days as it moves across Andromeda, passing near the Andromeda Galaxy around April 3. You can use Cassiopeia to point you to Beta Andromedae and from there to the comet. The map shows the sky facing northwest about one hour after sunset. Comet and galaxy brightness are exaggerated for the sake of illustration. Stellarium

Did you capture this event, too? Let us know, or upload your images to our Flickr page.

April 1, 2013April 26, 2016 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 24^th.

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 5^th, 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 19^th.

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 +6^th 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).

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 +4^th magnitude star may be easily visible in the dawn, a 3^rd or even 2^nd 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 13^th. An interesting grouping occurs as the planet Mercury passes only a few degrees from the comet from April 15^th to April 17^th. Having just past greatest elongation on March 31^st, 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 7^th and 8^thwhich may also provide for the first sighting opportunities from low north latitudes around these dates.

The Moon reaches New phase on Wednesday, April 10^th 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 25^th, 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 20^th and cross the plane of the ecliptic on April 22^nd 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 +6^th 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 9^th, 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 28^th 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!”

March 25, 2013April 26, 2016 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).

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).

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 8^th, 2006 and will happen next on May 9^th, 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).

Mercury will show a maximum illumination area of 38.5” square arc seconds as seen from the Earth March 30^th on just before reaching its greatest elongation west of the Sun on March 31^st 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 2^nd, the closest this has occurred date-wise since April 8^th, 2006. This won’t be matched again until March 24^th, 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 8^th 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 10^th. Mercury reaches superior conjunction opposite to the Earth and on the far side of the Sun on May 11^th, 2013, and will again head into the dusk skies for its next greatest eastern elongation on June 12^th.

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!

March 20, 2013April 8, 2018 by Bob King

Keeping up with Comet PANSTARRS through the end of March

Multiple exposures of Comet PANSTARRS taken on March 19 were stacked to create this amazing image. The field of view is about 6 by 4 degrees. Details: Leica-Apo180mm lens at f/4. Click to enlarge. Credit: Michael Jaeger

Wow – what an image! Michael Jaeger’s photo of Comet C/2011 L4 PANSTARRS on March 19 resembles those taken by the orbiting Stereo-B spacecraft. Check out this video (and the one below) to see what I mean. Most observers using binoculars and telescopes are seeing the comet’s head, bright false nucleus and a single plume-like tail.

Michael Jaeger of Stixendorf, Austria has been shooting beautiful comet images since 1982. Credit: Michael Jaeger

Careful photography like Jaeger’s reveals so much more – two bright, broad dust tails and three shorter spikes. One of the dust tails peels off to the left of the comet’s head, the other extends upward feather-like before splitting into two separate streamers. There are also several narrow, spike-like tails due to various excited elements and gas emissions from the comet’s icy nucleus.

Video of Comet PANSTARRS made from pictures taken by NASA’s STEREO-B spacecraft on March 13, one of two spacecraft that orbit ahead and behind Earth monitoring solar activity on the sun’s farside.

Michael Jaeger of Austria has been shooting pictures of comets since 1982. His images always reveal details that entice visual observers to go out and look for more than what first meets the eye. Last night I got my first look at the comet through a telescope and was delighted at the sight of its smooth, luminous tail and brilliant yellow false-nucleus. The false nucleus is the bright spot visible in the center of the PANSTARRS’ head; in 10×50 binoculars it looks like a star. Through a telescope it’s a fuzzy, yellow pea. Buried deep within the false nucleus is the icy comet nucleus itself, vaporizing in the sun’s heat and shrouded by its own dust.

Comet PANSTARRS last night March 19, 2013 in a setting with white pines. Details: 300mm lens, f/2.8, ISO 800 and 3-second exposure. Credit: Bob King — Comet PANSTARRS last night March 19, 2013 in the company of white pines. Details: 300mm lens, f/2.8, ISO 800 and 3-second exposure. Credit: Bob King

The comet has faded in the past week or two from 1st magnitude – equal to some of the brightest stars – to about magnitude 2.5 or somewhat fainter than the stars of the Big Dipper. In very clear skies, it was still dimly visible with the naked eye about 40 minutes after sunset low in the northwestern sky. I only knew where to look after first finding the comet in 10×50 binoculars. The tail points straight up and stretches nearly 2 degrees in length once the sky gets dark enough to increase contrast and before PANSTARRS sinks too low. I kept it in view for nearly an hour from a wind-whipped location north of Duluth, Minn.

The comet at 64x through a 15-inch (37cm) telescope on March 19, 2013. The pale yellow false nucleus highlights the smooth, curved tail. Illustration: Bob King

Through the telescope the nucleus blazed yellow from sunlit dust. Set inside the comet’s sleek, smooth head it reminded me of a lighthouse beacon shining through the mist. Gorgeous! The tail trailed bent back to the northeast with a slight arc. I highly recommend setting up your telescope for a look at PANSTARRS, if for no other reason than to see the beauty of the false-nucleus within the finger-like tail.

Use this map to find Comet PANSTARRS now through March 31. It depicts the sky facing west-northwest 30 minutes after sunset. The comet’s height remains fairly steady at about 10-14 degrees but it moves steadily northward (to the right). The yellow circles represent the sun’s position every 3 days. It also moves northward but more slowly. One fist equals about 10 degrees of sky. Created with Chris Marriott’s SkyMap software — Use this map to find Comet PANSTARRS now through March 31. It depicts the sky facing west-northwest 30-40 minutes after sunset. The comet’s height remains fairly steady at about 10-14 degrees but it moves steadily northward (to the right). The yellow circles represent the sun’s position every 3 days. It also moves northward but more slowly. One fist equals about 10 degrees of sky. Created with Chris Marriott’s SkyMap software

You can use the chart to help you find the comet for the remainder of the month. It shows the comet’s position every 3 days now through March 31 from mid-northern latitudes, specially 42 degrees north (Chicago, Ill.). If you live in the northern U.S., the comet will be in approximately the same positions but slightly higher in the sky; in the southern U.S. it will be a little lower. Notice the “15 degree” altitude line. If you set the bottom of your fist flat on the horizon, the 15 degree line is a fist and a half above that level.

Boulder Panstarrs from Patrick Cullis on Vimeo.

Time lapse video made by Patrick Cullis showing Comet PANSTARRS setting behind the Flatirons of Boulder, Col. on March 19. As you watch, notice how the comet appears against the sky background and the direction it moves toward the horizon – both clues to help you find it.

The map compensates for the sun rising later each night and shows the comet’s height above the horizon when the sun is 7.5 degrees below the horizon. 7.5 degrees corresponds to about 30 minutes after sunset. Notice that the sun moves northward (to the right) just like the comet does over the next couple weeks but more slowly.

A compass has two sets of markings. One shows the basic directions N, S, etc. Those directions are subdivided into degrees of azimuth seen in the outer ring. Credit: Wikipedia

See those yellow numbers along the map’s horizon? Those are compass bearings called azimuths. If you have a compass, dig it out and give it a look. Every compass is marked in degrees of azimuth. 270 degrees is due west, 285 degrees is a fist and a half to the right of due west, 315 degrees is exactly halfway between due west and due north. North can be either 360 degrees or 0 degrees. Azimuths are simple way to subdivide directions to make them more precise.

Comet PANSTARRS very low in the northwestern sky shortly before setting last night March 19. Details: 300mm lens, f2.8, ISO 3200 and about 4 seconds. Credit: Bob King — Comet PANSTARRS very low in the northwestern sky shortly before setting last night March 19. Details: 300mm lens, f2.8, ISO 3200 and about 4 seconds exposure. Credit: Bob King

The next time it’s clear, bring your binoculars and a compass (if needed) and find a location with a great view of the western sky preferably down to the horizon. Use the map along with the compass bearings to guide your eyes in the right direction. You can also use the sun’s position below the horizon to point you to the comet by angling up from the lingering glow at the sunset point. Remember to first focus your binoculars on the moon, cloud bank or star before attempting to find PANSTARRS. There’s nothing more frustrating than sweeping for a fuzzy comet with an out-of-focus instrument.

March 18, 2013December 23, 2015 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).

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 19^th 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 1^st 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 19^th	11:40UT/7:40EDT	Waxing	East Asia/Australia
1116	April 3^rd	3:20UT/23:20EDT*	Waning	Africa/Europe
1117	April 17^th	23:47UT/19:47EDT	Waxing	Eastern North America
1117	May 2^nd	16:19UT/12:19EDT	Waning	Central Pacific
1118	May 17^th	10:51UT/6:51EDT	Waxing	East Asia/Australia
1118	June 1^st	4:31UT/0:31EDT	Waning	Western Africa
1119	June 15^th	21:21UT/17:21EDT	Waxing	South America
1119	June 30^th	16:04UT/12:04EDT	Waning	Western Pacific
1120	July 15^th	7:49UT/3:49EDT	Waxing	Australia
1120	July 30^th	3:16UT/23:16EDT*	Waning	Africa/Western Europe
1121	August 13^th	18:50UT/14:50EDT	Waxing	South Atlantic
1121	August 28^th	14:27UT/10:27EDT	Waning	Central Pacific
1122	September 12^th	9:50UT/5:50EDT	Waxing	East Asia/Australia
1122	September 27^th	2:00UT/22:00EDT*	Waning	Middle East/East Africa
1123	October 11^th	19:52UT/15:52EDT	Waxing	Atlantic Ocean
1123	October 26^th	14:12UT/10:12EDT	Waning	Central Pacific
1124	November 10^th	10:03UT/5:03EST	Waxing	East Asia/Australia
1124	November 25^th	3:14UT/22:14EST*	Waning	Africa/Europe
1125	December 10^th	00:57UT/19:57EST	Waxing	Western North America
1126	December 24^th	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 17^th.

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 1^st and Last Quarter Moon in the daytime.

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 1^st 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).

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.

March 16, 2013December 23, 2015 by Ken Kremer

Comet Pan-STARRS Wows Over Holland

Comet Pan-STARRS thrills Dutch observers of the Night Sky on March 15, 2013 shortly after sunset. Shot with a Canon 60D camera and Canon 100/400 mm lens, exposure time 15 seconds, ISO 300 Credit: Rob van Mackelenbergh

Comet Pan-STARRS thrills Dutch observers of the Night Sky on March 14, 2013 shortly after sunset- note the rich hues. Shot with a Canon 60D camera and Canon 100/400 mm lens, exposure time 2 seconds, ISO 800. Credit: Rob van Mackelenbergh
See viewing guide and sky maps below
Update – see readers photo below[/caption]

Comet Pan-STARRS (C/2011 L4) is exciting amateur astronomers observing the night sky worldwide as it becomes visible in the northern latitudes after sunset. And now it’s wowing crowds in Europe and all over Holland – north to south.

Check out the beautiful, richly hued new photos of Comet Pan-STARRS captured on March 14, 2013 by Dutch astrophotographer Rob van Mackelenbergh.

“I took these photos in the southern part of the Netherlands on Thursday evening, March 14, at around 7:45 pm Dutch time with my Canon 60 D camera.”

“I was observing from the grounds of our astronomy club – “Sterrenwacht Halley” – named in honor of Halley’s Comet.”

Comet Pan-STARRS is a non-periodic comet from the Oort Cloud that was discovered in June 2011 by the Pan-STARRS telescope located near the summit of the Hawaiian Island of Maui.

The comet just reached perihelion – closest approach to the Sun – on March 10, 2013. It passed closest to Earth on March 5 and has an orbital period of 106,000 years.

Comet Pan-STARRS from Holland on March 15, 2013 at about 7:45 PM, shortly after sunset - Canon 60D camera, Canon 100/400 mm lens, exposure time 15 seconds, ISO 300. Credit: Rob van Mackelenbergh — Comet Pan-STARRS from Holland on March 14, 2013 at about 7:45 PM, shortly after sunset – Canon 60D camera, Canon 100/400 mm lens, exposure time 2 seconds, ISO 800. Credit: Rob van Mackelenbergh

“Over 30 people were watching with me and they were all very excited, looking with binoculars and cameras. People were cheering. They were so excited to see the comet. But it was very cold, about minus 2 C,” said Mackelenbergh.

The “Sterrenwacht Halley” Observatory was built in 1987 and houses a Planetarium and a Celestron C14 Schmidt-Cassegrain telescope. It’s located about 50 km from the border with Belgium, near Den Bosch – the capitol city of southern Holland.

Comet Pan-STARRS was photographed from Sterrenwacht Halley - or 'Halley Observatory' in Holland. Credit: Rob van Mackelenbergh — Comet Pan-STARRS was photographed from Sterrenwacht Halley – or ‘Halley Observatory” in Holland. Credit: Rob van Mackelenbergh

“It was hard to see the comet with the naked eye. But we were able to watch it for about 45 minutes altogether in the west, after the sun set.”

“The sky was completely clear except for a few scattered clouds near the horizon. After the comet set, we went inside the observatory for a general lecture about Comets and especially Comets Pan-STARRS and ISON because most of the people were not aware about this year’s pair of bright comets.”

“So everyone was lucky to see Comet Pan-STARRS because suddenly the sky cleared of thick clouds!”

“In the past I also saw Comet Halley and Comet Hale-Bopp, but these are my first ever comet photos and I’m really excited !”

“I hope to see Comet Pan-STARRS again in the coming days when the sky is clear,” Mackelenbergh told me.

Over the next 2 weeks or so the sunset comet may grow in brightness even as it recedes from Earth into darker skies. Right now it’s about magnitude 0.2.

So keep looking with your binoculars; look west for up to 1 to 2 hours after sunset – and keep your eyes peeled.

And report back here !

Ken Kremer

See a readers photo of sunset Comet Pan-STARRS below

Comet Pan-STARRS viewing graphic from NASA

Comet Pan-Starrs Sky Map. Viewing guide to find the comet low in the horizon after sunset.Credit: Spaceweather.com

Posted on March 11, 2013April 26, 2016 by David Dickinson
Update: Comet PANSTARRS Makes Its Northern Hemisphere Debut

Comet PANSTARRS as seen from Arizona on March 10, 2013. Credit and copyright: Chris Schur.

The first of three bright comets anticipated in 2013 became visible to North American observers this past weekend. Comet C/2011 L4 PanSTARRS is now currently visible low to the southwest at dusk, if you know exactly where to look for it.

Observers in the southern hemisphere have been enjoying this comet for the past few weeks as it reached naked eye visibility above 6^th magnitude around late February and began its long trek northward. Comet PanSTARRS is on a 106,000+ year orbit with a high inclination of 84.2° with respect to the ecliptic. This also means that PanSTARRS is currently moving roughly parallel to the “0 Hour” line in Right Ascension (The same point occupied by the Sun during next week’s Vernal Equinox on March 20^th) and is only slowly gaining elevation on successive evenings.

CometPANSTARRS from Michael Zeiler on Vimeo.

Observers in Hawaii and Mexico picked up PanSTARRS late last week, and scattered reports of sightings from the southern continental United States started trickling in Saturday night on the evening of March 9^th. We managed to grab Comet PanSTARRS low to the southwest on Sunday evening on March 10^th, about 30 minutes after local sunset.

Comet PanSTARRS seen from Hudson Florida on the evening of March 10th (Photo by Author).

We were surprised by the star-like appearance of the coma, about +1^stto 2^nd magnitude with a tiny fan-shaped tail. The comet was visible in binoculars only (I used our trusty pair of Canon 15×45 Image-Stabilized binocs for the task) and I couldn’t yet pick out the comet with the naked eye.

Several sightings westward followed. Clay Davis based in Santa Fe, New Mexico noted a visual magnitude of -0.5, saying that PanSTARRS was “Brighter than Mars” at magnitude +1 but “A challenge to keep in view.” Note that observer estimations of the brightness of comets can vary based on local sky conditions. Also, unlike a pinpoint star, the brightness of comets extends over its visible surface area, much like a faint nebula. The first sightings of the comet for many observers has been contingent on the weather, which can trend towards overcast for much of North America in early March. From our +28.5° northern latitude vantage point here just north of Tampa Bay Florida we had about a 10 minute window from when the sky was dark enough to spy PanSTARRS before it set below the local horizon.

Here are a few more images from Universe Today readers:

Comet PanSTARRS as imaged by Robert Sparks (@HalfAstro) on the night of March 10th from Tucson, Arizona. All Rights Reserved, part of the Universe Today photo gallery.

First views of Comet PANSSTARRS from Tucson, Arizona. Credit and copyright: Adam Block/Mount Lemmon SkyCenter.

Comet PANSTARRS from Puerto Rico on March 10, 2013. Credit and copyright: Efrain Morales.

To see the comet we suggest;

A clear uncluttered southwestern horizon;

A reasonably clear sky;

Binoculars.

First naked eye sightings of the comet for U.S. and European latitudes should be forthcoming over the next few evenings. PanSTARRS just passed perihelion yesterday on March 10^th at 0.3 Astronomical Units from the Sun (or 46.5 million kilometres, just inside the orbit of Mercury).

Comet PanSTARRS looking west at 8PM EDT the evening of March 12th from latitude 30 degrees north. (Created by the author using Starry Night).

And Comet PanSTARRS may put on its best show over the next few nights. The Moon reaches New phase today at 3:51PM EDT/ 19:51 UT and starts lunation number 1116. On the next few evenings, the slim crescent Moon will slide by Comet PanSTARRS. Look for the 2% illuminated Moon 5° to the lower right of the comet on the evening of Tuesday March 12^th. On the next evening, the 5% illuminated Moon will be 9° above Comet PanSTARRS on Wednesday, March 13^th. The age of the Moon will be 28 hours old on Tuesday evening and 52 hours on Wednesday the 13^th respectively, an easy catch. The Moonwatch website is a great place to check for those early lunar crescent sighting possibilities worldwide. Note that Comet PanSTARRS also passes less than 30’ from the planet Uranus (about the diameter of the Full Moon) on the evening of the 12^th at 8 PM EDT/24UT. +6^th magnitude Uranus may just be visible near the head of the comet using binoculars or a small telescope. Keep in mind, they just appear to be close as seen from our Earthly vantage point. PanSTARRS is currently 1.1 A.U.s from the Earth, while Uranus is on the other side of the solar system at 21 A.U.s distant!

Comet PanSTARRS looking west at 8PM EDT from latitude 30 degrees north on the evening of March 13th. (Created by the author using Starry Night).

PanSTARRS also crosses the Celestial Equator today on March 11^th and the Ecliptic on March 13^th. Observers from dark sky sites may get the added bonus of the zodiacal light, a true photographic opportunity!

Spacecraft studying the Sun are also giving us views of Comet PanSTARRS from a different perspective. NASA’s twin STEREO A & B spacecraft are positioned to monitor the Sun from different vantage points along the Earth’s orbit. Often, they see comets as an added bonus. Comet PanSTARRS has just moved into the field of view of STEREO-B’s Heliospheric Imager and has given us amazing views of the comet and the Earth in the distance over the past week.

The view of Comet PanSTARRS from NASA’s STEREO Behind observatory. (Credit: NASA/SECCHI).

From STEREO, the remarkable fan-shaped dust tail of PanSTARRS stands out in profile. The dust tail of a comet always points away from the Sun. Driven by the solar wind, a comet’s tail is actually in front of it as it heads back out of the solar system! An ultimate animation of Comet PanSTARRS just came to our attention today via @SungrazerComets on Twitter;

Animation of comet 2011 L4 PanSTARRS entering STEREO-B’s HI camera, note the twin ion/dust tail reminiscent of Hale-Bopp! (Credit: NASA/STEREO/NRL).

As of this writing, PanSTARRS seems to be performing as per predictions with an observed magnitude of around +1. The comet will continue on its northward trek, becoming a circumpolar object for observers based around latitude 50° north on April 2nd. Comet PanSTARRS should dip back below +6^th magnitude around April 15th.

Comet PanSTARRS as imaged by Mike Weasner from Cassiopeia Observatory in southern Arizona on the night of March 10th. Used with permission.

But this is but Act One in a forecasted three act cometary saga for 2013. Comet C/2012 F6 Lemmon will grace early dawn skies in April for northern hemisphere observers, and then all eyes will be on Comet C/2012 S1 ISON for the hoped for grand finale later this year. Interestingly, ESA’s Solar Heliospheric Observatory will get a look at this sungrazing comet as it passes through its LASCO C3 camera’s field of view. Clear skies, and may 2013 go down as the Year of the Comet!

-Check out photos of Comet PanSTARRS and more being added daily to the Universe Today’s Flickr gallery.

Posted on March 8, 2013April 26, 2016 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).

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 March 8, 2013December 23, 2015 by Bob King
A Guide to Help You See Comet PANSTARRS at its Brightest

Comet L4 PANSTARRS setting over Brindabella Ranges to the west of Canberra, Australia on March 5, 2013. The photo gives a good idea of the naked eye of the comet. Credit: Vello Tabur

This is the big week so many of us in the northern hemisphere have been waiting for. Comet C/2011 L4 PANSTARRS, which has put on a splendid show in the southern hemisphere, now finally comes to a sky near us northerners!

Sky watchers in Australia and southern South America report it looks like a fuzzy star a little brighter than those in the Big Dipper with a short stub of a tail visible to the naked eye. The comet should brighten further as it wings its way sunward. Closest approach to the sun happens on March 10 at a distance of 28 million miles. That’s about 8 million miles closer than the orbit of Mercury.

Though very low in the western sky after sundown, the comet should be visible across much of the U.S., southern Canada and Europe beginning tonight March 8.

Comet PANSTARRS will be visible through about March 19 for sky watchers living near the equator. Map is drawn for Singapore. All maps created with Chris Marriott’s SkyMap software

PANSTARRS’ low altitude presents a few challenges. Approaching clouds, general haziness and the extra thickness of the atmosphere near the horizon absorbs the comet’s light, causing it to appear fainter than you’d expect. A casual sky watcher may not even notice its presence. That’s why I recommend bringing along a pair of binoculars and using the map that best fits your latitude. Find a place with a wide open view to the west, focus your binoculars on the most distant object you can find (clouds are ideal) and then slowly sweep back and forth across the sky low above the western horizon

Comet PANSTARRS map for the southern U.S. March 6-21. Time shown is about 25 minutes after sunset facing west. Map is drawn for Phoenix, Ariz.

As the nights pass, PANSTARRS rises higher in the sky and becomes easier to spot for northern hemisphere observers while disappearing from view in the south. On the 12th, a thin lunar crescent will shine just to the right of the comet. Not only will it make finding this fuzzy visitor easy-peasy, but you’ll have the opportunity to make a beautiful photograph.

Comet PANSTARRS and the thin crescent Moon should make a striking sight together about a half hour to 45 minutes after sunset on March 12. Stellarium

The maps shows the arc of the comet across the western sky in the coming two weeks for three different latitudes. Along the bottom of each map is the comet’s altitude in degrees for the four labeled dates. The sun, which is below the horizon, but whose bright glow you’ll see above its setting point, will help you determine exactly in what direction to look.

One of your best observing tools and the one closest at hand (pun intended) is your hand. Photo: Bob King

A word about altitude. Astronomers measure it in degrees. One degree is the width of your little finger held at arm’s length against the sky. Believe it or not, this covers two full moon’s worth of sky. Three fingers at arm’s length equals 5 degrees or the separation between the two stars at the end of the bowl of the Big Dipper. A fist is 10 degrees. This weekend PANSTARRS will be 2-3 “fingers” high around 25 minutes after sunset when the sky is dark enough to go for it.

The northern U.S. is favored for this leg of the comet’s journey. Notice how the comet arcs up higher in the sky compared to the southern U.S. and especially the equator. Map drawn for Duluth, Minn. The comet will remain visible for many weeks. Earth is closest to PANSTARRS on March 5 at 102 million miles.

To find PANSTARRS, locate it on the map for a particular date, note its approximate altitude and relation to where the sun set and look in that direction. Assuming your sky to the west is wide open and clear, you should see a comet staring back. If you don’t find it one night, don’t give up. Go out the next clear night and try again. While Comet PANSTARRS will fade over the next few weeks, it will also rise higher into a darker sky and become – for a time – easier to see. I also encourage you to take out your telescope for a look. You’ll see more color in the comet’s head, details in its tail and an intensely bright nucleus (center of the comet), a sign of how fiercely sunlight and solar heating are beating up on this tender object.

Sound good? Great – now have at it!

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