Jim Shields and I decided to take a chance last night on Lake Sonoma, although the situation looked basically hopeless on the 80 minute drive up 101 at 3:30. The skies stayed heavily overcast until moonset and we were very close to giving up ... but the veil of clouds quickly pulled back from west to east and we hurriedly threw our scopes together, quite amazed at the transformation into a beautiful dark sky. The only other observer at the lake was Dick Flasck and we decided to set up our 17.5" scopes at the Gray Pine Flat lot.
I brought along a list and finder charts of a couple of PNe, including some oldies but goodies along with other difficult targets and started with NGC 246 and moved east. Unfortunately, a couple of hours later after working 1/4 of the way through my list the clouds rolled back in just as quickly as they had departed. Within a half hour it cleared again for more observing but clouded up again after another hour so we called it quits. But it was still well worth taking a chance on a very iffy night! Here are the more interesting planetaries I took a look at --
NGC 246 = PK 118-74.1
00 47 03.3 -11 52 19
V = 10.9; Size 240"x210"
At 100x, NGC 246 appears as a moderately bright, 3.5' irregular glow with a darker center and encompassing four stars including a 12th magnitude central star. Excellent contrast gain using an OIII filter, which sharpens up the edge of the roundish annulus and enhances the irregular surface brightness. The halo is brightest along the 270° arc running from SW to NE and is clearly weakest on the E edge of the halo. A mag 11.5 star is embedded at the NW edge of the halo 2.0' from center. The irregular central hole is much darker but faintly luminous. Also superimposed is a mag 12 star SW of the central star and a 4th star is just inside the eastern boundary. At 220x, the western 90° outer arc is brightest and there appears to be a knot embedded at the NE edge of the halo.
IC 351 = PK 159-15.1
03 47 32.9 +35 02 49
V = 11.9; Size 8"x6"
Picked up at 100x as an out of focus mag 11 "star". At 220x, this high surface brightness PN was clearly nonstellar and slightly oval with a hint of a sparkle (central star) at the center. At 500x, appeared as a small, well-defined disc, elongated 4:3 SW-NE, and ~7"x5". The quasi-stellar center was brighter with a small, fainter halo which seemed irregular. A couple of faint stars are close W and N. Located 3.5' NW of a distinctive trio of mag 10/11/13 stars with separations of 32", 36" and 58".
NGC 1501 = PK 144+6.1
04 06 59.4 +60 55 15
V = 11.5; Size 56"x48"
At 100x, this moderately bright PN was irregularly round, 1' diameter, weakly annular with a faint glimpse of the central star. There was a good contrast gain with the OIII filter and the image was crisp-edged, slightly elongated SW-NE and the small, darker center was more evident. Excellent view at 220x with the faint central star (mag 14.4) clearly visible. The surface brightness was irregular with an unevenly brighter outer rim. The central star was visible steadily at 280x and the overall surface brightness was mottled or "clumpy" (brighter on W and NE rim), darkening in the center.
Kohoutek 2-1 = PK 173-5.1
05 07 08.7 +30 50 03
V = 12.0; Size 132"
Faintly visible at 100x as an irregular ill-defined glow with couple a stars superimposed including a mag 12 star at N edge. Situated between a mag 10.5 star off the NE edge and a mag 12 star off the SW side. Excellent contrast gain using an OIII filter and appeared elongated roughly 3:2 SW-NE, ~90"x60", although the edges are not well-defined. Possibly brighter along the west side. The outline was noticeably irregular at 220x using a UHC filter and may reach the star off the SW edge. Nearby is mag 9 SAO 57652 located 5' SE.
Be careful about looking up this object is amateur software. The original position given in the Catalogue of Galactic Planetary Nebulae (also called the PK catalogue) was 1.0 minute of RA too far east and 2' too far south (off by 15'!) So, this object is misplotted on the U2000 as well as TheSky. The classification status is also unclear and it's listed as a bright nebula (Lynds Bright Nebula 809)! To further confuse the situation, it is catalogued as a galaxy (PGC 16765) at the correct position!!
Kohoutek 1-7 = Abell 10 = PK 197-14.1
05 31 45.5 +06 56 09
V = 14.0; Size 35"x32"
17.5" (1/8/00): easily picked up at 100x using an OIII filter as a fairly faint, round disc. There was a better view at 220x and a UHC filter with the 25"-30" disc having a crisp edge. No annularity or interior stars were visible. Also viewed unfiltered as a weak, round glow although filters provided a significant contrast gain. A mag 13.5 star lies 0.9' SSE of center. The PN is situated between two mag 12 stars oriented SW-NE [3.5' separation] and is 5' WSW of an unequal double [mag 10/13 at 11"].