by Jay Freeman
Despite the looming presence of that great natural source of light pollution, the Moon, I took Harvey, my Celestron 14, to the Dinosaur Point boat launch area, adjacent to San Luis Reservoir, on the evening of 19 January, 2002. I hadn't had the big Schmidt-Cassegrain out in months, but I had run my current small-telescope deep-sky program -- doing Herschel-400 surveys with several instruments -- well into the morning hours, so I decided to see whether even under a five-day Moon, it was still true that APERTURE WINS. It was, and it did, but it took a little bit of black art to make it happen.
I showed up at the site while it was still light, bearing two giant pizzas from Pinocchio's No. 2, in Gilroy. These were much appreciated, and earned me half a yummy veggie sandwich and a lot of guilt points in compensation. There was little left for the local raccoons, and since none of them showed up, I ended up taking the remains home for breakfast the next morning. My cats couldn't quite figure out what to do with pizza with garlic and herbs on it. Anyway, while telescopists munched, I set up Harvey, and prepared to observe.
I had been letting objects accumulate on my "cats and dogs" observing list, and wished to tackle some of them. Many of these objects are not necessarily a problem in their own right in bright sky; for example, on the list were a number of "non-existent" Herschel clusters, places where William Herschel had reported a star cluster but where modern astronomy does not find one. Star clusters bear magnification well, and thus often show up easily in moonlight. On the other hand some of the things I wanted to look at were faint galaxies, or structural features in faint galaxies, and all of them were too faint to appear on Millennium Star Atlas, or I would have logged them in my previous observing program.
Fortunately, I knew that the nuclear regions of many galaxies are bright enough so that they, also, stand magnification well. I have routinely used exit pupils in the range of 1.5 mm to observe galaxies, with great success. Thus, one of my favorite galaxy-watching magnifications with Harvey is 244x. An exit pupil that small is enough to darken the background field to a reasonable level even with a quarter Moon lighting up the sky.
On the other hand, even if the object bears magnification well, allowing the background field to be darkened, there is still the problem of all that moonlight illuminating the eyepiece, the back of the telescope, and the ground nearby. It's difficult finding faint fuzzies when the ambient light is bright enough to read your charts. Yet as I said, arcane practitioners of esoteric crafts realize that true black art provides a possible solution, and I was willing to pay the price to test it.
The price was a few dollars for a yard of durable, opaque black cloth at Joanne's Fabrics, for an observing hood. I don't mean fancy sewing, I just draped the material about me as required. The kind of black art I had in mind dates from the days of vaudeville, when bright lights facing the audience and black velvet used liberally on the far side of them could hide all manner of unseen things, and result in strange special effects and illusions, all in real time and all close at hand. It was mere coincidence that with my black wrapper drawn about my head and shoulders and my handses in my pocketses, er, hands in my pockets, I looked like a ringwraith. Honest. Yesss, honesssst.
I started the evening with five of those "non-existent" clusters. For two, nominally NGC 1498 and 2167, I saw nothing at 196x (using a nice Brandon 20 mm wide-field eyepiece) that looked like a cluster. The other three, NGC 1908, 1909, and 2306, varied from unconvincing clumps of a few stars to a rich part of a rich field. "Freeman's cluster" lies yet undiscovered, just like Isildur's bane.
Then I tried some sterner fare. UGC 12914 is on Millennium, but not its companion, UGC 12915. I did spot both of them at 196x, with use of the observing hood. Next was a small cluster of galaxies grouped about NGC 3, in Pisces. I had seen several before -- the ones plotted on Millennium -- but somewhere I had dug up notes that suggested two more should be visible; namely, NGC 4 and NGC 7837. The background at 196x was a bit brighter than I liked, so I dropped in a 12 mm Brandon, for 326x. That gave me the usual problems, of where did the reference stars go, and since I had left my Palantir at home, I had to swap eyepieces between the 12 mm Brandon and the 40 mm Vernonscope Erfle that I usually use for low-magnification viewing, to find them. Eventually I pinned down NGC 3, and nailed four other galaxies (including two I hadn't seen) via offsets from it. The observing hood was invaluable for this work, after a few minutes under it I was amazed how dazzling the moonlight appeared when I took it off. I took the precaution of keeping my observing eye closed when it was not shielded by the hood.
Back at 196x, I looked for UGC 1807, 25 arc-minutes NNW of NGC 891, and thought I had found it, but when I checked the Digitized Sky Survey (DSS) a few days later, I found that I had been deceived by a few stars near the position, the actual galaxy is very low in surface brightness. I will have to try again on a darker night. We wants it. I also could not see long, slender UGC 1999 in Aries, or planetary EGB 1, also known as PK 124+10.1. This last is huge -- several arc minutes in size, and faint. I did not expect to see it in the conditions that prevailed, but I found one star near the charted position that "blinked" with my Orion UltraBlock filter, and wondered whether I had perhaps found its central star. No luck, the DSS showed I was a few minutes of arc off. We wants that, too.
I did spot UGC 2023, in Triangulum, as well as NGC 1023A, a companion to NGC 1023 that lies a few arc minutes east. My final toughie target of the evening was NGC 2366, a galaxy that contains an HII region brighter than all the rest of it. I had logged the "galaxy" before, thinking the HII region was its bright nucleus, but with knowledge of what to look for, at 196x I could see not only the bright nebulosity but also the thin wisp of the rest of the galaxy, trailing off to the northeast.
I spent the rest of the evening reviewing brighter stuff -- lots of aperture really does win, even in moonlight. Alas, the seeing was poor, on viewing the Trapezium at 196x I had only occasional glimpses of star "E", not a trace of "F", and no temptation to try more magnification.
How pleasant to find that interesting deep-sky work can be done under a considerable Moon. My observing hood is likely to become a valuable and well-used piece of apparatus. It may even become -- dare I say it -- precious to me. Yessssss, precioussssss...