Saying Goodbye to Coma

by Albert Highe

Observing Report for July 24-26, 2003 - Plettstone

The Weather just said "no" to astronomy - as in no clouds, no wind, no humidity, and no jackets required. Conditions couldn't have been better on Thursday and Friday. Daytime temperatures approached 100F under beautifully clear blue skies. By 9PM the temperature dropped to the low 80's F and never got below 72F during the night. We observed in nothing more than short sleeved shirts (and, of course, pants). The %RH never got above 50%, making for nice dry conditions. Transparency was very good to excellent. Seeing was very good, often showing pinpoint stars at 400X.

Conditions looked very promising on Saturday as well. However, at 11:30PM clouds quickly moved in, making it a short night.

Scope: 17.5" f/4.5 ultralight Eyepieces: mostly 7mm and 9mm Nagler T6, but occasionally the 5mm Tak LE when seeing permitted.

Brief Summary and Selected Highlights This was my last chance to hunt for galaxies in the Coma Cluster, Abell 1656, until it appears again next year. By 9:45PM, the sky grew dark enough to observe galaxies that were only 45 above the horizon. By 11PM, even the eastern most galaxies were too low to observe. So I was able to spend a total of four hours on the Coma Cluster during the three nights.

Abell 1656, the Coma Cluster, is by far the richest and most dense galaxy cluster. Over the past several months, I've spent approximately 60 hours creating a target observing list and finder charts for this cluster of galaxies. Until recently, my list only included members within approximately 1 of the center. Galaxies are so dense in the central region that only six finder charts sufficed. The list now includes galaxies as far as 4 from its center. For locating the outlying galaxies, I also generated an additional 55 finder charts. Finder charts are typically 0.25 to 0.5 wide and are created by downloading DSS images and labeling them in Photoshop.

My target list contains 723 objects with photographic magnitudes as faint as 17.5. I found 76 new galaxies this past week, bringing the total to 271. Based on radial velocity data, only 18 galaxies are likely not gravitationally bound to the cluster. Based on my results so far, I expect to increase the number observed to over 400 next year.

On Thursday, I added 18 galaxies to my list for Abell 2151, bringing the total to 69. But I decided this was too intense after hunting down galaxies in Abell 1656. So, for the rest of the night I relaxed and enjoyed looking at bright favorites and leisurely hunted down galaxies using Uranometria. I also took the more leisurely approach on Friday and Saturday nights after studying Abell 1656.

Mars was very good both Thursday and Friday. In the 17.5" at 285X, the southern polar cap was startlingly white. I could make out subtle darker features across the planet's surface.

My favorite chain of galaxies is in Pisces and it rose to a nice viewing location by 2AM. The chain is comprised of NGC's 379, 380, 382, 383, 387, 386, 385, 384. I've found all of them before. However, Friday night provided the clearest and brightest view I have ever seen of them. Even the faint NGC387 was rather "easy". I could hold it with averted vision 80% of the time.

Once again, many thanks to Michelle for being such a wonderful host.