by Matt Tarlach
Last Sunday night, 4/2/2000, Ken Sablinsky and I enjoyed a night of observing and imaging from the site near Fiddletown in the Sierra Foothills. We had many fine views of a variety of objects, including Hickson galaxy groups and some interesting planetary nebulae. I recently relocated my notebook, which had slipped under the seat of my truck, and can finally post a report for those who are interested in such things. Scope used was a 12.5" f6 Astrosystems truss dob with mirror by Steve Swayze. Limiting mag was 6.3, seeing 4/5 dropping suddenly to 3/5 at about 2 AM.
I arrived at the site about a half hour before sunset, plenty of time to set up, collimate, and enjoy the beautiful sunset. The observing area was covered in a carpet of green grass, and there was very little dust, unlike what I've experienced there later in the Summer. As twilight deepened I took a peek at Saturn and Jupiter, low in the West but still pretty in the steady air that often characterizes this site immediately after sundown. When darkness finally arrived I warmed up by visiting M42, and some familiar targets like M97 (the Owl) and NGC3242 (the Ghost of Jupiter). The view of M42, perhaps my last this year from a good site, was very striking, with fantastic amounts of detail that was enhanced somewhat by my new 2" OIII filter. Removing the filter and pushing the power to 160x with my new 12mm Type 4 Nagler, the 5th and 6th stars in the Trapezium popped into view. The Nagler is a wonderful eyepiece...this was my first experience with it at a dark site, and it quickly became my favorite ocular, occupying the focuser tube for about 2/3 of the session. It is wonderfully sharp, with excellent contrast similar to the 12mm Radian. I thought the sky background appeared nearly as dark, and contrast almost as high, as in the 9mm Nagler despite the lower magnification in the 12.
After marvelling at Orion's ornaments, I turned to the galaxies of Spring rising in Leo. As I starhopped across the constellation, I panned across many small galaxies that Ken and I had fun identifying with the help of Uranometria. I've been observing a lot with the Short Tube 80 lately, and I think working with small apertures really trains your eye - these little NGCs were popping out easily, just like Messiers in the smaller scope. When we finally arrived at the big Messiers, they looked like real showpieces! Spiral structure was visible in both M65 an 66, and NGC 3628 with its big dark bar was very impressive. In total I logged 16 galaxies in Leo, before taking on the Hickson groups. Ken was busy capturing CCD images with his own rig, and would come over for a look whenever I sounded really excited about something.
Last year I clipped Steve Gottlieb's excellent article on Hickson compact galaxy groups from the pages of Sky and Tel, and tracking down each of the groups he listed has been one of my observing goals. Sunday night I moved 4 steps closer to that goal:
Hickson 44 in Leo is a fairly large and easy (as Hicksons go!) group of 4 galaxies. The largest and brightest of them was substantial enough to be swept up at 160x (12mm Nagler), and at 212x (9mm Nagler) showed a dust lane. The other three galaxies appeared elongated but otherwise featurless; the faintest still detectable with direct vision. Hickson 51 is more compact and quite a bit tougher; after viewing at 212x I logged it as "At least 5, poss. 7 galaxies in tight group oriented generally East-West." Checking Steve's notes, I see he calls HGC51 a quintet, and describes two of the members as "very faint" and "extremely faint," as seen in his 17.5"....perhaps I mistook some field stars for faint galaxies.
Hickson 57, also in Leo, is known as Copeland's Septet, and was one of the more daunting challenges of the night. It is very compact, just a few arc minutes across, and only the brightest member (NGC3753) could be seen directly as a small elongated smudge. As with HGC51 I stepped up to 212x with the 9mm Nagler to break it up into its components. After perhaps 15 minutes of averted vision and scope jiggling, I logged: "4, poss. 5 faint galaxies with several faint stars or small galaxies invloved." After Copeland's Septet (should I call it a Quartet, after confirming only 4 galaxies?) I turned to HGC61 in Coma Berenices, which turned out to be one of the highlights of the night. Known as "The Box," this group is composed of 4 elongated galaxies arranged in a neat quadrangle, and showed up nicely in the 12.5". All four galaxies could be seen with direct vision at 160x, though the faintest was right on the cusp.
Moving down to Corvus we got a nice look at NGC 4038/38A, the Antennae, a bright pair of interacting galaxies that starred in one of my favorite Hubble photos. Nearby is NGC4361, an odd object listed as a planetary in all my resources but which to my eye more resembled a big face on galaxy with a bright core. (When I first posted this report to sci.astro.amateur, David Knisely replied confirming this is a PN, and says he calls it the "Lawn Sprinkler." I agree it's a fitting appellation for this diffuse, swirling, interesting nebula.)
One of my preplanned targets for the night was Omega Centauri, and as I waited for it to culminate I made a quick pass through Virgo and Coma, stopping to linger on M64 (the Black Eye, looking quite bruised) and the always awesome NGC4565. Then I toured some favorites in the Northern sky: M51, M81 and 82, and M101 were all beautiful. The view of M81 in particular was one of the best I can recall, with the wispy spiral arms easily visible. As a beginner it took me many observations to see those arms, probably beacuse I was looking for the wrong thing...I was trying to resolve the "bright" central part of the galaxy into arms, as with M51. Actually the arms are fainter, gauzy structures extending outwards from the central area; now that I know what to look for I see them much more easily.
Checking my watch and my planisphere, I saw that Omega was approaching due South, the highest it would climb above my Southern horizon. Unfortunately that wasn't high enough....the treeline to the South of the observing site blocked the view from my dob. I turned to the Short Tube 80 on a tall tripod, and viewing straight through Ken and I were able to catch the mighty cluster as it skimmed the horizon. It was a huge, fat glow with only a few stars resolved, as seen through all that air. We turned the same scope to M13 rising in the East for comparison...it was much more resolved but dimmer and less than half the size, a reminder of the spectacle that Omega must be when seen from a more southerly locale. Returning to the southern sky we found NGC5128 in the Short Tube as a small glow....unfortunately even this was too low for the 12.5." I did catch M83 in the big scope: a large, rich, spiral glow, about the same size but brighter than M101 and with a bright central core.
At this point we took a little break, retiring to the lounge chairs for some refreshments, conversation, and casual binocular observing. We also did some limiting magnitude checks, using the sector charts linked to Bill Arnett's web page. My limiting mag estimates are usually on the low side, I think because my astigmatism hampers naked eye vision more than telescopic viewing. In the past when I've done limiting mag estimates at TAC events, I've been 3 to 5 tenths behind the deepest gazers...nevertheless on this night I got to 6.3 zenithal limiting mag without trying too hard. This is good, but not the best I've obtained from this site. Though we remained dew-free throughout the night, the sky seemed grayer than I've seen in the past and I suspect there was some high altitude water vapor up there interfering.
About the time we returned to the scopes, after perhaps a 45 minute break, an odd warm wind kicked up out of the West, and while transparency remained good the seeing deteriorated noticeably. We were still able to pick up perhaps 2 dozen members of the Coma cluster of galaxies, and detected "lumpy darkness" in the position of the Hercules Galaxy Cluster. The planetary nebula Abell 37 rewarded our patient hunting by revealing its faint round form, with a suggestion of annularity. Another planetary, IC 4593 in Hercules,was much brighter and showed a bright central star. We wound up the evening with the NGC6302, the Bug Nebula in Scorpius, and interesting object that reminds me of the Crab Nebula, though with more easily seen filamentary detail.