The DARC Observatory 8/11/07

by Steve Gottlieb

The main structure is mostly completed and at either end are two imposing circular structures that will house 22-foot domes. I set up my 18-inch in one of the vacant structures and in the other Lee and Robert set up a 16-inch LX200 and a wonderful pair of 150mm (6-inch) binoculars on a parallelogram style mount. If you're curious about this ambitious project, see http://darcobservatory.org/

The evening was clear and dark -- perfect for hunting faint galaxies and planetaries. Here's a selection of the objects I took a look at in the evening.

Abell 44
18 30 11.4 -16 45 28
V = 15.8; Size 63"x39"
Picked up at 73x using an OIII filter as a very faint, small glow attached to a mag 12.5 star. Best view at 115x and OIII filter and visible continuously with averted version as a fairly small, 35" round disc with a star superimposed on the west edge. Situated in a very rich star field just 35' WNW of the rich cluster NGC 6645 and roughly two degrees ESE of the Swan Nebula.

Abell 66
19 57 31.5 -21 36 46
Size 295"x241"
At 73x with an OIII filter this huge Abell planetary appeared very faint, irregularly round, ~3' diameter, very low surface brightness. Visible nearly continuously with averted vision, though only occasionally the outer edge of the halo appeared crisply defined. A mag 13 star is at the NE edge and a number of fainter stars are superimposed without a filter.

Abell 68
20 00 10.8 +21 42 58
V = 15.2; Size 40"x37"
It required some effort to identify this faint Abell planetary at 115x and OIII filter, but once I pinpointed the location it was visible as an extremely faint, fairly small, round disc, ~35" diameter with a very low, even surface brightness. Visible roughly half the time with averted vision. Located just 1' N of a mag 10.5 star (first of 4 stars in a 4' string SW to NE) and 1 degree north of M27!

Abell 77
21 32 10.2 +55 52 43
V = 14.0; Size 67"x50"
At 115x and OIII filter Abell 77 appears as an extremely faint, slightly elongated disc of very low surface brightness and a fairly well defined 60"x50" halo. Visible ~50% of the time with averted vision, though with concentration can hold steadily for extended periods.

Campbell's Hydrogen Star
19 34 45.2 +30 30 59
V = 10.5; Size 13"x10"
Picked up at 174x as a mag 10.5 star with an orange-red color. Excellent contrast gain by blinking with a H-beta filter! At 280x and 450x the central star is clearly surrounded by a small, thin red halo or ring, ~7" in diameter. Although I've viewed this object before, this was the first time it appeared as a thin ring! This planetary, along with IC 418, are in a very elite group that display a reddish halo.

Minkowski's Footprint Nebula
19 36 18.9 +29 32 50
V = 12.0; Size 8"x3"
Initially identified unfiltered at 220x as a hazy or soft "star" just 30" following a brighter mag 10 star. The "Footprint Nebula" has a fairly high surface brightness and it easily held 450x. At this power the brighter "sole" was clearly non-stellar, though only ~5" in diameter with a much fainter, small extension (the "heel") to the SE. Located 2.2' SSW of a mag 9 star in a rich Milky Way field.

This is a very low excitation young proto-planetary with extremely weak OIII lines and does not respond to filtration.

Egg Nebula
21 02 18.8 +36 41 41
Size 24"x6"
The "Egg Nebula" was viewed at 450x as this object is quite small but has a high surface brightness. This bipolar proto-planetary consists of two small round knots oriented SSW-NNE with the brighter component on the NNE end. This 12th magnitude knot appears ~10" in size with an occasional star or stellar point at the center. Just SSW is a much fainter mag 14 knot, ~6" in size and the two components are encased in a very faint, elongated halo so the dimmer component just stands out individually. Located just 4' east of mag 8 HD 200371.

Abell 76
21 30 03.8 -02 48 32
Size 0.4'x0.2'
At 260x this misclassified Abell appeared faint, very small, round, ~20"x15", very weak concentration. Located 2.4' W of a mag 9 star and 1' SSE of a mag 14 star.

Abell 76 was originally listed by Abell as a regular, symmetrical planetary nebula, 13" diameter having the appearance of a ring with gaps. But it was shown in 1971 to have a radial velocity of 3424±40 km/sec, yielding a distance of roughly 30 Megaparsecs. In 1982 it was classified as a "collisional ring" galaxy, so you know longer see it in the Abell PN list.

IC 1318 (NW section)
20 16.9 +41 49
Size 50'x20'

Last month I took a close look at a couple of sections ("Butterfly Nebula") of the huge Gamma Cygni complex. This night I focused on probably the brightest piece of the IC 1318 nebula. This section was easily visible at 12.5x in the 80mm finder using a H-beta filter.

At 73x with a UHC filter, it appeared very extended SW-NE or WSW-ENE, roughly 40'x8' and passes through a mag 8 starThe brightest portion is to the NE of the mag 8 star and a number of similar mag stars are involved with this portion. Removing the filter, this section was still visible though the highest contrast was using a UHC filter. To the SW of the star, this river of nebulosity takes a mild bend and flows more towards the south. Another fainter section of nebulosity (not included in the size estimate) spreads out to the NNW of the mag 8 star. IC 1318(b) is located roughly 2° NW of Gamma Cyg (Sadr).

Abell S963
This little-known Abell cluster is located a mere 45' NNW of M30. It includes NGC 7103 and 7104 as well as IC 1393 and 5122 and is located at a distance comparable to the Hercules Galaxy Cluster (nearly 500 million light years) I also picked up a couple of fainter "anonymous" galaxies with the unwieldly designations 2MASX J21394847-2235031 and 2MASX J21403915-2229208. Here's the dominant member:

NGC 7103
21 39 51.4 -22 28 26
V = 12.6; Size 1.4x1.2; Surf Br = 13.0
Largest and brightest of 6 members viewed in galaxy cluster ACO S963. At 260x appeared fairly faint, fairly small, slightly elongated, ~30"x25", broad weak concentration. Occasionally I glimpsed a nearly stellar galaxy (2MASX J21394761-2228171) just 0.9' W. NGC 7104 lies 4' NE, IC 5122 4' NNW, and IC 1393 6' NE. --CalStar 2007