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After a number of last minute decisions on observing the past few months due to dicey weather, it was nice to head out to the Sierra foothills under clear skies and good prospects last Saturday night (15 May 1999). When I arrived friends Jim Shields and Ray Cash were already setting up and I listened to reports from the other observers on Friday nights conditions - clear and dark, but breezy and cold. Fortunately, the temperature had warmed up on Saturday and the wind had died down, so it was shaping up for an excellent evening.
While it was getting dark we waited around for an iridium satellite flash in the north that went off as expected. During darkening twilight I took a look at Comet Lee before it sunk below the trees southwest of the observatory. Very nice - even in a 16x80 finder. At 100x in my 17.5" the coma was quite bloated and there was a trace of a fan-shaped tail. Next up was supernova 1999by in NGC 2841 which was evident at low power embedded in the NW extension, a bit brighter than 14h magnitude. It was fully dark at this point, so it was off to fainter deep sky stuff. Here are a few highlights --
With listed dimensions 938"x636", Abell 35 is a huge, low surface brightness ancient PN. On this night it was immediately seen at 100x using an OIII filter surrounding the mag 9.6 central star (a white-dwarf companion is actually the ionizing star). It appeared roughly 6'x4' extended SW-NE with the mag 9.6 offset NE of center. The brightest part of the nebulosity is near this star and in the vicinity just SW. The nebulosity doesn't quite reach a mag 10.5 star situated 5.5' SW of the central star but it seems to extend to a mag 11.5 star [2.7' following the central star]. Although the surface brightness is very low it is clearly irregular and leaves you wishing for larger aperture.
On the opposite end of the size scale is IC 3568 in Camelopardalis, located far enough north (82.5 degrees dec), that you can comfortably use high power on an undriven dobsonian. This is a multi-shell shrimp, so you need to use high power if possible. At 220x (no filter) it appeared as a very small, high surface brightness disc, ~10" diameter with a mag 13.5-14 star close off the W edge. At 380x, the disc is concentrated to a quasi-stellar nucleus, but it's difficult to distinguish the central star due to the surrounding high surface brightness haze. Surrounding the central region is a much fainter outer round shell which increases the diameter to 15"-20". Unfortunately, seeing was not steady enough to use higher powers.
On the brighter springtime planetaries is NGC 4361 in the sail of Corvus. The view at 100x easily shows off the 13th magnitude central star surrounded by a moderately high surface brightness halo ~1' in size which gradually brightens towards the center. With averted vision, the halo increases to roughly 90"x60", extended SW-NE. There's a tantalizing extension or hook on the SW end of the PN, which I confirmed the next day on the DSS image (bipolar structure).
NGC 4395 is a chaotic galaxy in Canes Venatici dominated by several bright HII regions. At 100x, the large low surface brightness glow is clearly clumpy with a couple of faint knots evident on the east side of the haze. At 220x, the glow of the galaxy loses its identity and several nonstellar knots and a couple of very faint superimposed stars dominate the view. The brightest HII region is NGC 4401, ~25" in size with a second smaller knot (NGC 4400) close south. The core of the galaxy appears as an ill-defined low surface brightness glow, larger than the individual HII knots. On the SW side of the core is a third difficult knot, about 15" in diameter (NGC 4399) requiring averted vision to confirm.
A recent project has been trying to glimpse the "brighter" members of the Shakhbazian catalogue of compact clusters of compact galaxies. "Brighter" is somewhat of a joke - most of these clusters have brightest members 18th magnitude and fainter, but still there a few groups that are very interesting in dark skies with 16" and larger scopes.
Shakhbazian 202 is a tiny group of six nearly stellar 15-16th magnitude galaxies nearly lost in the glow of mag 6.7 SAO 82246 (12h 19.9m +28 25) about 15' north of 9 Comae. A couple of months ago I had pinned down four of the galaxies, but the sky was perfect for an assault on the remaining dim jokers. Only a couple of the brighter members are visible without much effort and these are just 15" dim knots. To see all six required 280x to 380x and lots of patience for moments of good seeing for the fainter 16th magnitude members to pop out. Needless to say, the bright nearby star is a major hassle.
Shakhbazian 16 is a remarkable compact linear chain of five virtually stellar 16th magnitude galaxies in Draco (16 49.2 +53 25) also catalogued as Arp 330. Once again a fairly bright star (mag 9) is practically situated on top of the group to provide additional frustration. Two of the members, Shkh 16-1 and Shkh 16-2 were visible at 280x with a little effort but I spent the next hour waiting for glimpses of the remaining three members. I didn't give up, though, until I was convinced I had glimpsed all five. It was an exhausting but satisfying way to end the evening.