by Randy Muller
The moon, the weather and my employer all cooperated to provide me a couple good deep sky viewing opportunities during the week between Christmas and New Year's Day. On the Feast of Stephen (Tuesday, Dec. 26), I feasted with Steve (of Gottlieb) on random deep sky delights from Fiddletown, California, at an elevation of about 2600 ft. in the Sierra foothills.
On Thursday, Dec. 28, I binged on Hickson Compact Galaxy Groups from the Henry Grieb Observatory, 5284 ft in the Sierras, which is the subject of this report.
Observing with Steve is always literally an eye-opening and mind-opening experience. During the course of the evening, Steve asked me what my observing program was. This is not an uncommon question. Mark Wagner also once asked me this question at Lassen, and I eventually told him that the NGC was my observing list, which is more or less true, though mostly less.
I couldn't give this same answer to a major contributor to the NGC/IC project, whose observing program really has been the NGC (as well as countless other obscure catalogs), so I was forced to admit to Steve that I really didn't have anything planned, other than just observing new stuff and pushing my scope to its limit. We then discussed various possibilities for me, like reobserving objects I had already observed in my 10", since they will look totally different in my 18". I mentioned that I was working on a casual Messier survey for the 18" in my "spare time".
This conversation re-stimulated my thinking on observing programs. Why have a program at all? For me, it can make the difference between having a so-so night, and having a great night. It can make the difference between seeing a lot of stuff in one night, and having long idle periods filled with "what should I look at now?" thoughts.
I recalled that I had intended to do a survey of Hickson Compact Galaxy Groups with my as yet undelivered 18" in June of 2000. I had even gone to the trouble of printing out the complete list of HCGs from Jim Shields' excellent web site Adventures in Deep Space (see reference below). This catalog contains groups of four of more galaxies in close proximity. Stephan's Quintet (Hickson 92) is perhaps the most famous member of this catalog. If you like Stephan's Quintet, you will find more like it, both more and less challenging, in the Hickson catalog.
I had filed these sheets in my logbook, ready to use any time I was out, and then never used them! I made sure I was going to use them tonight. I drove up the hill eager to explore this new catalog.
I assumed the tarmac would be clear because it hadn't snowed since it had been blocked 11 days earlier. In spite of this, I prepared for snow in the clothing that I wore., particularly my snow boots. I knew it would not be a fun night observing with cold feet.
I could not have been more wrong about snow on the tarmac. When I arrived, there was snow 1-2" thick on the tarmac, and 0-4" thick on the road going in. I quickly decided I could set up on the snow itself. The only problem was getting to the tarmac on the road. I knew this is one reason I bought the vehicle I did to carry my 18"-it has four wheel drive. I was a bit nervous about getting stuck, since I didn't have chains or snow tires or shovels or any other snow equipment in the car.
I took a deep breath and drove in. It was a little slippery, but I made it in easily, and I laughed at myself for being worried about it. I went ahead and set up in the snow, and I had to be extra careful because the surface was a bit slippery and I didn't want to drop my 50 lb. mirror which is difficult enough to carry when the footing is sure.
Lest anyone think I am a little crazy, it wasn't even cold. It was probably in the high 40s, which made the presence of the snow even more puzzling.
A short while after I arrived, an owner of one the observatories near HGO arrived in his pickup truck. Judging by the sounds of him driving back and forth on the road, I could tell he was having trouble getting in, but he finally made it. Sometime later, Allan Keller showed up on foot. His pickup truck was back on the road, and he made a valiant effort to get in, but finally failed. That was too bad, because it was to be a night to remember.
As the night wore on, the icy snow became harder and firmer. I noticed that the "spotlight effect" was a lot less pronounced this night than it had been a year ago at the same location. The "spotlight effect" occurs in snow at night with no lights other than the stars. I seem to be standing in a slightly brighter spot of light, and the snow around me dims the further away it is. The "spotlight" follows me as I walk around on the snow, which causes an eerie feeling.
Apparently it works best with fresh powder snow, and less well with week-old icy snow.
This turned out to be a night for the astronomical record books, one of my best nights observing ever. My observation of NGC 542 was the 1000th distinct object I've observed since I started in this hobby in August, 1996 with my then-newly acquired 10" dob. I observed a total of 39 new objects-all galaxies. While writing my observations of Hickson 95, a bright green meteor as bright as Venus dropped from the sky in the south, to my left. It caught my eye, and I turned and watched it. It's always thrilling and surprising to see stuff like that.
I waited until it got dark enough to start seeing the faint galaxies. While I waited, the moon showed a lovely crescent in the general vicinity of Venus.
I decided to begin with the most westerly objects and slowly make my way eastward. Due to the presence of clouds, could not go too far westward, and had to interrupt my sequence at one point. I then finished up in the south once again.
This is a very nice, big, interesting group with 5 members. All the members together were visible only at 226x. This was a great group to start with.
NGC 7550: At 87x (26mm plossl), this was fairly small, fairly bright, diffuse halo and stellar core. Forms neat and obvious right triangle with NGCs 7547 and 7549.
NGC 7547: At 133x (17mm plossl), a bit fainter, round, non-stellar center.
NGC 7549: Big, more diffuse and somewhat fainter than 7550 and 7547. Seems round. Whoops! A mag 15 satellite just went through the field!
NGC 7553: At 226x, (10mm plossl), very faint, somewhat concentrated in the center.
NGC 7558: Extremely faint, diffuse halo, concentrated in the center.
This extremely compact group has 7 members, but I was able to observe only three of them. Located only 32 arc minutes SE of Hickson 93, they appeared as a large, irregular glow within a triangle of stars at 87x. At 226x, the glow appeared elongated and irregular. At 301x, I was able to separate the glow into two components.
NGC 7578a: At 301x (7.5mm plossl), very faint, diffuse.
NGC 7578b: Seems brighter than 7578a. Appears to have a stellar center, but the galaxy as a whole is much smaller than 7578a.
PGC 70943: Extremely faint-at limit of vision. Very elusive glow
This small group has 4 members, of which I could only see 2, and one of those was very intermittent. At 226x (10mm plossl), the group was visible only as a general glow.
NGC 7609: Using 301x, it appears very faint, relatively "large" diffuse oval.
MCG +01-59-048: Extremely faint, visible only 20% of the time as seeing varies. Very small.
At 87x, this 4 member group is gorgeous! The bright galaxies are arrayed in a semicircle around a mag 9.5 double star (HJ 2116), although I did not notice the duplicity. This is a very nice, bright group. It should be relatively easy in a 10" scope, and NGC 835 is probably even visible from my backyard.
NGC 835: At 226x, it was oval with a strong central concentration.
NGC 833: Almost touching NGC 835, much fainter, but still very bright. Much less concentrated in center.
NGC 838: About the same brightness as NGC 833, slightly fainter, but more concentrated in center than NGC 833.
NGC 839: Bigger, but fainter and more diffuse than NGC 838.
At 87x, this 6 member group shows as a lumpy uneveness and elusive glow. At higher power, I was able to see 5 of these, and while they make a nice group, they are very dim and unimpressive.
UGC 1624: At 226x, oval, fairly dim and small, diffuse, no stellar center
UGC 1620: Slightly dimmer, more concentrated than UGC 1624
UGC 1617: Somewhat fainter, less concentrated center, oval
MCG +00-06-033: Very faint diffuse blob
UGC 1618: Very faint oval mass
At 87x, this is a spectacular group of 4 galaxies! NGC 542 was difficult at this magnification.
NGC 536: At 226x, very bright, relatively large, oval, concentrated center. There seems to be a stellar feature a few arcseconds N of the central condensation. Thinking it might be a supernova, I later checked out a Digital Sky Survey image of this object, and saw that the star is indeed there.
NGC 531: Less oval than 536, less bright and more diffuse.
NGC 529: Fairly bright, round, very concentrated center.
NGC 542: Extremely faint, intermittent ghostly presence.
Only the brightest member of this group of 5 galaxies was obvious at 87x. Even using 226x, only two of the members were visible.
NGC 2783a: At 226x, easy to see. Very concentrated center, almost stellar. Fairly bright and round.
NGC 2783b: Very faint and very elongated.
This is a group of 5 galaxies, of which I was able to see 3.
NGC 1214: At 226x, round, fairly bright, smaller than nearby non-member NGC 1208, very concentrated center.
NGC 1215: "Large" (comparitively), diffuse, stellar center.
NGC 1216: Very small, stellar center.
I was able to see 3 out of the 4 members of this group.
MCG +00-12-051: At 226x, a fairly bright oval with a concentrated center, right next to a star.
MCG +00-12-054: Slightly dimmer than MCG +00-12-051, round and very concentrated in the center.
PGC 15624: Extremely faint. Visible only intermittently.
At 87x, this very tightly packed 4 member group blended into one glow near a star. Ultimately, I was able to see only one member at high power.
NGC 1741: At 301x, I still only viewed the combined light of NGC 1741a, 1741b and PGC 16573. It was a strange-looking irregular diffuse glow.
| Date | December 28, 2000 4pm-1:30am (Dec 29, 00:00-9:30 UT) |
|---|---|
| Location | Henry Grieb Observatory, 36.85N 121.57W |
| Instrument | Starmaster 18" f/4.3 dob-newt |
| Oculars | 7.5, 10, 17, 26mm Sirius Plossls; 1.15x Tele Vue Paracorr |
| Seeing | 6/10 Steady but fuzzy stars. Seeing variable. |
| Transparency | 8-5/10 Partly cloudy with long periods of good clarity |
Hickson References:
The following is based on and mostly quoted from Jim Shields' Hickson page, describing the source of the Hickson catalog:
The source of the Hickson catalog is Paul Hickson's Atlas of Compact Groups of Galaxies. His original paper provides catalogue data and identification charts for 100 very compact groups, including some 436 galaxies, based on a systematic search of the POSS red prints. To qualify for inclusion a compact group had to meet 3 rigid criteria: 1) population--at least 4 members, 2) compactness--surface brightness greater than 26.0/arcsec2 averaged over the smallest circle containing their geometric centers, 3) isolation--to exclude condensations in rich Abell galaxy clusters.
Jim's Hickson page is located at http://www.angelfire.com/id/jsredshift/hickson.htm
The whole catalog can be found at http://www.angelfire.com/id/jsredshift/hickcatalog.htm
A subset of more interesting Hickson objects is located at http://www.angelfire.com/id/jsredshift/hicklist.htm
Adventures in Deep Space is located at http://www.angelfire.com/id/jsredshift/
Ray Cash has a very nice cache of Hickson material, including lots of observations at http://members.aol.com/anonglxy/hickson.htm