This past weekend I made a presentation to the CAS at Lowell Observatory about Visually Observable Comets for 2006. Preparing it turned out to be an excellent education for me in ways I hadn't expected. I wanted to generate ideal observing times and animations of the paths of C/2005 E2 McNaught, C/2006 A1 Pojmanski, and 73P/Schwassmann-Wachmann. I hadn't counted on how demanding that would be. Planning months in advance what the observation windows are for a bunch of wiley comets means accounting for sidereal rotation of the sky night by night, evolving sunrise/sunset times, beginning/end of astronomical twilight, phase and rise/set time of the moon, and then the comet's changing position in the sky. 73P, the one with the greatest potential in mid-May of this year, is also going to be dueling with a waxing nearly-full-moon when it reaches its brightest. So getting a good look at it while it's showing its best, will mean observing the week prior to full moon during the dwindling window between moonset and dawn astronomical twilight.
In addition to discussing when and where to observe these three comets, I also wanted to review observations of some recent comets, and discuss observing methods, particularly sketching. I got permission from some generous amateur astronomers to display their excellent sketches for those portions of the presentation. If you are interested in seeing some detailed, wonderfully crafted comet observations and sketches, check out these sites:
Bill Ferris' Cosmic Voyage
Eric Graff's Sketch Gallery(Look for Comet Machholz!)
Kiminori Ikebe's Deep Sky Observations(See the Solar System section)
Eric Jamison's Comet Sketches
Wes Stone's Comet Observations (See also his Hyakutake and Hale-Bopp Compilations.)
Seiichi Yoshida, author of Aerith.net kindly gave permission for me to use the sky chart and magnitude graphs on his informative site. If you are looking for up-to-date information of current and upcoming observable comets, Mr. Yoshida's site is the place to look. It's an excellent resource.
Photographer Ctein (pronounced K'Tine) from California also gave me permission to use some beautiful photographs of C/1996 B2 Hyakutake and 1P/Halley to open and close the presentation. (Check out these pages on his site for some amazing space program photography: Gallery 8, Gallery 7, Gallery 3.)
I had a fantastic experience corresponding with these folks. Their willingness to share their efforts so willingly made the whole process very rewarding.
I'm in search of some server space for the comet path animations I put together. But in the meantime, here is info on the three comets discussed at the meeting. There are others coming up, but these are the brightest for now.
C/2005 E2 McNaught
I've already made one observation of this evening comet. It remains visible in the evening sky at +35° Latitude for a couple months as it cruises through Pisces to Aries and eventually Perseus before getting too low to observe. It's at maximum brightness next week around Mag. 10. Follow this link to Aerith.net for charts. Follow this link for an ephemeris.
C/2006 A1 Pojmanski
This will be a morning comet that begins to appear above the southestern horizon, SE of Sagittarius in late February/early March (for +35° Latitude). It will be at peak brightness the night of February 24/25 at possibly Mag. 5.0-5.5. That's pretty nice, although from this latitude we'll be catching it on the downswing. It will move quickly to the eastern arm of Aquila by March 4 with no moon interference. By dawn astronomical twilight, it will have risen to 14° above the horizon, as visible from Flagstaff, AZ. On that morning, it could be visible to the naked eye at 5.2-5.7 magnitude. By the time it reaches Delphinus on March 11, at Mag. 5.7-6.2, it will be competing with a nearly full moon that sets just as astronomical twilight begins. By March 26, it is in Lacerta, at mag. 7.3-7.8 and the moon isn't interfering. It keeps cruising toward the north, ending up in Cassiopeia, where on May 1, it's dwindled to mag. 10.2-10.5 or less. It also begins to show low along the northern horizon after dusk. Follow this link to Aerith.net for charts. Follow this link for an ephemeris.
73P/Schwassmann-Wachmann
This periodic comet has a lot of potential, but also a hefty contender in the full moon. It will pass within .08 AU from the Earth on May 12th. That's about 12 million km/7.5 million miles--32 times the distance to the moon. This pass will put it high in the midnight sky during the weeks preceding this close pass. It has the potential to reach naked eye visibility at mag. 3.5 during this flyby. Currently it is in the constellation Virgo at mag. 14. By March 25, it will be in Bootis at potentially mag. 10.5 during the new moon. By April 22, it will have drifted to Corona Borealis at possibly mag. 7.2 again with no moon interference. By April 29, it really starts racing across the sky and is in Hercules, at a possible mag. 6.1 with no moon problems. From here until May 8, every night is a dwindling opportunity to catch the comet between moonset and dawn. If the comet performs well enough to compete with the moon, it will be superimposed over M57 on May 8 at 3 AM UT, which works out to May 7 at 8:00 PM Mountain time. It could be mag. 4.9 that night. By May 12/13, it will be in Vulpecula at possibly Mag. 4.5-3.5, but fighting a full moon, which is a huge bummer. As the comet proceeds eastward, it begins to rise later and later until the morning of May 22 when it rises at 2:00 am in the constellation Pisces. It could be around mag. 5.1 and will be 5° north of a crescent moon that is 5 days shy of new. I'm not sure how bright that crescent will be, but I'll be interested to see if the conjunction is visible in binoculars. For the remainder of the Summer, it settles into the constellation Cetus, eventually rising at 11:30 pm by August 19th at a possible mag. 11.1.
I should mention that the comet will present a 2nd component that is about 3 magnitudes fainter than the main component, although I'm not sure how much separation there is between them. A third component seen during its last passage hasn't been recovered yet, and may have dissipated the last time around. This passage will be so close that we may see an outburst Bootid meteor shower accompany it in May/June. This should be an interesting and tricky comet to follow. I'm hoping for some good sketch and photo opportunities. Follow this link to Aerith.net for charts. Follow this link for an ephemeris.
