Lake Sonoma 9/10/07 (Monday night)

by Steve Gottlieb


I met Bob Douglas last night for a really pleasant evening of observing at Lake Sonoma. Weather conditions were nearly ideal - warm, clear, dry and completely calm. Seeing was also very good and I was able to get a clean split on STF 2764 in Cepheus -- at low power this appears to be an attractive 7" double of mag 8/9 stars, but at 323x the fainter star was just split into an 0.75" pair of mag 9.5 stars and the close pair was cleanly split with dark space between at 452x.

Unfortunately, the transparency was noticeably degraded (perhaps a magnitude) due to particulates still floating around from the fires both to the north and south. It was particularly poor along most of the horizons where extinction really dimmed the skies. Looking within 25 degrees of the horizon, it felt like I was back home in light-polluted Albany. Also the light dome from Cloverdale towards the NW was much higher than usual as it must have been reflecting off the particles in the atmosphere. Still, with 40 degrees or so of the zenith, the sky looked reasonably good and that's exactly where I parked my scope for the evening.

To gain back some of the lost transparency, I jacked up the magnification on a number of planetaries which darkened the background. Here's a few of the better objects in my 18-inch Starmaster.

NGC 6891
20 15 08.8 +12 42 15
V = 10.4; Size 12"x10"

Visible as a faint "star" at 12.5x in the 80mm finder and easy to verify as a planetary by blinking with an OIII filter. In the 18-inch at 225x, the bright, blue disc of high surface brightness surrounds the central star. At 300x the very bright oval disc of 8"x6" diameter is surrounded by a fainter, round outer envelope that increases the diameter to ~15". With direct vision the central star is visible embedded in the center of the high surface brightness disc. A mag 12.5 star lies 1' WNW and a mag 13 star is a similar distance ESE with N6891 nearly at the midpoint.

NGC 7008 = Fetus Nebula
21 00 32.8 +54 32 36
V = 11.0; Size 98"x75"
The "Fetus Nebula" is a fascinating annular planetary and best viewed at high power. Using 452x the oval halo is elongated SSW-NNE, ~85"x65". Most striking is a bright, 25" knot on the NNE end that is irregular in surface brightness with a very small brighter condensation near its south end. The SW quadrant of the planetary is also brighter in an elongated region and it is weakest on the E and SE edge facing the wide double star. In the darker center a mag 13.5 central star is visible and a second fainter mag 14 star is near the NE edge. Also another mag 14 star is just off the west edge. N7008 is situated just north of a mag 9.3/10.2 double (h1606) at 18" oriented N-S. It was faintly visible in the 80mm finder at 25x using an OIII filter.

NGC 7026 = Cheeseburger Nebula
21 06 18.6 +47 51 08
V = 10.9; Size 29"x13"
At 565x the "Cheeseburger Nebula' is easily resolved into two small, elongated knots oriented ~E-W and with both lobes slightly extended ~N-S. Both knots are lively or mottled and slightly tapered in shape. Both contain stellar nuclei or points near their centers with the western nucleus slightly easier. The eastern lobe is barely larger and brighter. The lobes are nearly tangent but just separated by a darker lane and both lobes are encased on a common halo. At 807x, the two lobes were clearly separated by a dark lane (the Cheeseburger's "patty") oriented SSW to NNE. A mag 10.5 star is off the NE side, less than 30" from the center. Located 13' NNW of mag 4.6 73 Cyg.

NGC 7027
21 07 01.5 +42 14 10
V = 8.5; Size 18"x11"
Visible as a mag 8.5-9 "star" at 12.5x in the 80mm finder and easily identified using an OIII blink. At 175x in the 18-inch, appears as a small, very high surface brightness oval with a blue-green color. At 450x, this planetary is elongated 3:2 NW-SE, ~18"x12" and has an unusual bipolar appearance with two lobes. The 10" NW component has a very high surface brightness and contains a quasi-stellar brighter knot on its west edge. A fainter lobe juts out towards the SE and is slightly smaller (~8"). At 565x the SE lobe seems incomplete as if it was partially obscured and two lobes are encased in a thin outer envelope. The view was fascinating at 807x with a feel of a 3-dimensional object - the brighter NW lobe being closer and the partially overlapping SE lobe extending away in space. At this power both lobes were clearly irregular in shape and surface brightness.

NGC 7048 = PK 88-1.1 = Hb 9 = PN G088.7-01.6
21 14 14.2 +46 17 28
V = 12.1; Size 62"x60"
At 280x unfiltered appears as a moderately bright disc that is slightly elongated ~N-S, ~65"x60". A mag 10.5 star lies just off the south end (42" from center) and a mag 13 star is off the north end (60" from center). Appears slightly brighter along the west edge and to a less extend the east edge, giving a weak annular appearance. A faint star is right at the NE edge of the rim and on the NW side. An extremely faint star is also sometimes visible at the NNW edge of the rim. Located 3.3' ENE of mag 8.3 SAO 50601.

NGC 7662 = Blue Snowball
23 25 53.9 +42 32 05
V = 8.3; Size 32"x28"
Viewed this gorgeous double shelled planetary at 807x in good seeing. The outer envelope is a sharply defined 35"x25" oval, oriented SSW-NNE. Roughly half-way to the center is a remarkable, thin oval ring oriented SW-NE (slightly offset in orientation to the outer shell) of very high surface brightness. This annular ring is brightest along a 90 arc along the south side and is alo enhanced along a shorter arc at the west edge of the northern part of the ring. The ring fades and appears broken with a gap along the west to WNW edge. Inside the ring is a darker oval hole that is weakly luminous.

Steve


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