May 23, 2009: Closing in on a 30-year observing project

Steve Gottlieb

I started in astronomy with an inexpensive 60mm refractor that was gathering dust in a garage. In the mid-70's, this modest scope "discovered" the phases of Venus, followed the nightly dance of the Galilean moons and stumbled across many deep sky objects by random sweeps of the sky. But the mount was shaky; the eyepieces had a very narrow apparent field or unusably high power and the aperture was too small to see many deep sky objects as much more than dim smudges.

An Edmund 6-inch f/6 fork-mounted reflector was a huge upgrade (particularly viewing on camping trips at high elevation dark sites including Yosemite, Zion, Bryce and the Grand Canyon) and by 1978 I had completed the Messier list along with a fair number of showpiece objects. At this point, I had a bad case of observing fever and in 1979 purchased a C-8, followed by a 13.1-inch in 1981. Monthly observing sessions at Fremont Peak in the early 1980's provided a deep sky fix. As far as targets, I'd just pick a constellation and try to find everything reasonably bright in Burnham's or follow up on whatever objects were mentioned by Walter Scott Houston in his monthly Sky & Tel column.

As I started to pick off hundreds of 12th and 13th magnitude galaxies with the 13-inch, I had the foolish idea it would be cool to observe the entire NGC – all 7840 objects compiled by John Dreyer in 1888 – and I probably had no more than 7000 to go! What appealed to me is that the NGC appeared right before the use of photography, so all of the entries were discovered visually. Although no less than 172 different astronomers contributed observations in the NGC, I knew William and his son John discovered the vast majority of the NGC entries using an 18.7-inch speculum-metal mirror that was probably inferior in light-gathering ability to the 17.5-inch scope I purchased in 1984. So, at the rate I was going I naively assumed it would only take a few more years (yeah, right).

One major stumbling block was finding accurate data and finder charts of faint objects in the early and mid-1980's (Skalnate Pleso Atlas of the Heavens and later Sky Atlas 2000.0 only included brighter deep sky objects and Burnham's lists ended around 13th magnitude). Fortunately, I had access to the UC Berkeley Astronomy library and discovered a slew of professional galaxy catalogues such as the UGC, CGCG and MCG as well as a complete set of Palomar Observatory Sky Survey (POSS) prints. After an observing session at Fremont Peak or Fiddletown in the Sierra foothills, I'd bring my notes over to astronomy library and scrutinize the POSS intently using a 10x Loupe to help identify objects and compare notes. I started to make rough sketches of interesting galaxy fields on the POSS, but then purchased several 11x14 contact prints from the Cal Tech bookstore in Pasadena which contained the fields of the Virgo Cluster, Perseus Cluster, Hercules Cluster etc. as these were by far the best finder charts available for tackling galaxy clusters (no online DSS available!).

A second major stumbling block was the numerous errors and conflicting identifications I kept running across in the professional and amateur literature, particularly with fainter NGC galaxies. This made it nearly impossible to correctly identify many of the objects I was logging and the observing project was looking way to overly ambitious. I wasn't ready to give up, though, and began corresponding with professional astronomer Harold Corwin at the University of Texas, who had a special interest in the historical accuracy of the NGC and already solved some of these riddles. As snail-mail evolved into e-mail several amateurs/pros with a similar interest in the history of visual astronomy joined together on the NGC/IC Project and completed a historically correct revision of the entire NGC and IC. This made it possible to correctly ID hundreds of misidentified objects found in amateur sky-plotting software as well as professional catalogues.

So where do things stand after working on this project (along with other observing projects such as Hickson compact groups, Abell galaxy clusters, Abell planetaries, Palomar globulars, etc.) for 30 years? Out of the 6888 NGC entries that are theoretically visible from Northern California sites (roughly +38 degrees latitude), I've now whittled down the list to just 77 remaining objects! And now if I said the NGC observing project will be completed in a year or two, I wouldn't sound foolish.

I set a southern cut-off of -42 degrees declination from bay area observing sites. At that declination, objects culminate on the meridian at 10 degrees elevation and are accessible from a dark site with a good southern horizon. The last couple of years have been spent mopping up the faintest galaxies of the NGC with my 18-inch Starmaster, scouring the southern horizon well below -40 degrees dec (those who observe at Willow Springs often joke when I'm lying on the ground observing) as well as trying to identify non-descript Milky Way fields that were logged by the Herschels but really don't stand out at the eyepiece.

If anyone else is crazy enough to want to repeat this massive project here are a few suggestions. Detailed computer generated or photographic finder charts are a necessity. Commercial atlases will not do the trick in rich regions, even the large–scale close-up charts in the Uranometria 2000.0. If you're using sky-plotting software set it to display or print fainter galaxies than you expect to see. At the faint end of the NGC (generally mag 15-16), there are large numbers of similar dim galaxies that were missed that could be mistaken for NGC objects. With rich galaxy clusters, I often like to use large-scale images that clearly identify objects packed into a small region.

Depending on the observing lists, catalogues, atlases, software and on-line resources you use, once you journey beyond the well-traveled destinations of deep sky objects, it's very easy to run into conflicting and erroneous identifications of objects. Historically corrected NGC identifications, data and images are available at NED (http://nedwww.ipac.caltech.edu/), a complete historically revised NGC and IC is available at http://www.klima-luft.de/steinicke/ngcic/ngcic_e.htm and all of my visual observing notes are at http://www.astronomy-mall.com/Adventures.In.Deep.Space/steve.ngc.htm. The NGC/IC Project site has been offline for a while, but has just been resurrected with the help of Chris Watson at the new address http://www.ngcicproject.org/ so historically corrected identifications, finder charts, source material and much more is available again.

For this project to work in a lifetime, stick with one region of the sky and work on it thoroughly, instead of a "hit the highlights" approach and then have to return numerous times to log all the objects. Of course, I've returned to most of the eye-candy objects many times to look for additional details, particularly with interesting deep sky objects. I also take log fairly detailed notes, so I can compare observations taken years apart, possibly with different equipment and almost certainly under different observing conditions.

What were the most challenging NGC objects to track down? As I mentioned earlier, there are numerous Milky Way fields that are not detached clusters, but rather "enhancements" in the Milky Way that caught the eye of William or John. Fortunately, although many of these are not visually striking, either the positions or reference to a brighter star can at least help to identify the field. Using a 26-inch refractor (f/14.9) made by Alvan Clark, observers at the Leander-McCormick Observatory in Virginia discovered 476 galaxies, mostly in the south equatorial zone and a number of these are very challenging, isolated galaxies that were at the limit of my 18-inch. Also, William Parsons (the 3rd Earl of Rosse) discovered a couple of hundred faint galaxies using the 72-inch Leviathan he built at Birr Castle in Ireland. These objects were found by surveying galaxies previously found by John and William Herschel. Because the Herschels missed these objects, they tend to be quite dim and some are at the extreme visual end of the NGC.

What's next? After several extended observing trips to Australia, I've made a pretty large dent in the NGC objects below -45 degrees declination, and have fewer than 300 southern NGC's left. Many of these are in the neighboring LMC galaxy, which is only fully accessible from the southern hemisphere. I'm hoping a few more trips to the southern hemisphere will finish up most of these remaining 300 and complete the entire NGC!