I spent two nights observing in Delphinus over the last week. One at my home, under suburban skies in Novato CA, with an 8" Discovery Dob, and one at Lake Sonoma with a 17.5".
I am placing the two reports sequentially, as there are a couple of comparable observations of the same target in the different telescopes.
October 11, 2001
Technical data Date/Time: 11 Oct 2001 - 2200-0015 PDT (0500-0715 UT) Location: Novato CA. 38N 122.6W Elev 500' Weather: 14°C Temp, 53 Humidity Instrument: 8" F6 Dobsonian Oculars: Pentax XL eyepieces Seeing: LM 5+, good steadiness, and excellent transparency
This was a quick evening observing session, nice clear skies and no moon. After preliminary glances at parts of the sky with bright Messiers, and allowing my eyes to dark adapt, I settled in to continuing exploration of Delphinus which is nicely situated for comfortable (seated) observing from my back deck.
First up was Gamma Delphinus, a pretty double star easily split at 65x and quite colorful at 110x, with a golden, almost orange, primary and a greenish tinged secondary, that looks to be about a magnitude fainter.
Next on the list was NGC 6891, planetary nebula, a delightful little ball of ionized gas which does indeed look spherical with a bright center (12th Mag star). To find it I needed a high power view (170x), and charts to put me in the right place. The nebula stayed bright in an OIII filter, and remained fuzzy under the sharpest focus, but I could not discern any specific color.
Keeping with the planetary nebula theme my next target was the "Blue Flash" Nebula, NGC 6905, which while not as bright as 6891, was easily three times larger and much easier to find. A scan with an OIII filter at 65x brought a glowing blob into view. Zooming in to 110x and 170x brings some of the structure into view. It is clearly asymmetric, circular in shape but brighter on one side. Averted vision helps bring the details out, as the nebula tends to fade under direct scrutiny.
I spent some time tracking down NGC 6928/6930 off the tail of the Dolphin to no avail, it was late and time to turn in.
October 13, 2001
Technical data Date/Time: 13 Oct 2001 - 2000-0130 PDT (UT -7, or 0300-0730 14 Oct 2001 UT) Location: Lake Sonoma CA, 38°43'N 123°02'W Elev ~900 (Grey Pine Flat) Weather: 23°C-19°C Temp 27-32% Humidity, no wind Instrument: 17.5" F5 Discovery Dob, +Telrad Oculars: Pentax XL eyepieces Seeing: LM 6+, transparency 7/10 after the clouds cleared
We had a great turnout at Lake Sonoma, with three 17" Dobs, three NexStar 11 GPS, two 15" Dobs, a C9.25, and a variety of smaller telescopes and binoculars. Several members of SFAA made the trip up from San Francisco, and from the East Bay. The viewing conditions were very pleasant with very low humidity and shirt sleeve temperatures, a steady atmosphere, but not such good transparency so viewing was a little soft.
Our usual haunt at Lone Rock was completely filled with equestrians, seriously filled up. There were well over a hundred horses, with associated transport, trucks, people etc. having a big two or three night event. We used the backup site, Grey Pine flat which is about 500' lower, and has a more southerly aspect, with a few trees in the west, and north. A light dome from Healdsburg and Santa Rosa to the south interferes with viewing a bit in that direction.
We spent a fair amount of time trading views over the course of the night, with the new NexStar-11s being quite popular. They are surprisingly quiet, and track very well. The OTA and fork arms are heavy, but easy to install on the supplied tripod, which looks very sturdy.
Even with a bit of socializing I was able to get to my observing list, and hit a few objects that I'd gone for in the 8".
Starting with NGC 6905 again, the "Blue Flash" has clear structure in the big scope and the central star shows up with averted vision. Moving up to 210x the view held up well, showing some nice structural variation in the outer rim, almost bubbly in appearance.
Steve Gottlieb was also looking at Planetary Nebulae, and we sidetracked each other with views NGC 7662 the Blue Snowball. This provided very nice views all the way up to 320x. With a nice central darker region, and some extension to the nebula, like a double shell. Approximately 30° separate the fainter shell from the semi-major axis of the brighter shell.
Back to Delphinus, and NGC 6928 which had eluded me in Thursday. It is a nice edge on and shows some core brightening and thickening along the disk. There are (at least) three galaxies in the view (NGC 6930 and NGC 6927), with a relatively easy direct view on 6930, but the dimmest needs averted vision to see. It is easily found by following a crooked chain of four field stars that runs between the bright galaxies. It may be possible to see 6928 in the 8" but probably not from my backyard.
NGC 6934 is a nice globular cluster which shows some interesting darkened regions around the halo of the cluster (at 100x), in rays outwards from the center, and arcs near the periphery. At 210x some stars resolve, but the majority remain clumps of fuzziness.
Once again Steve G. and I traded views on NGC 6956 and its companion galaxies. 6956 is a nice oval shape, adjacent to a pair of field stars. With his help I could see the dimmer companion galaxy which is due east of 6956, again with a pair of stars 'pointing' to it. We noticed an odd coincidence, that each of the galaxies has such a pair of pointer stars.
My final Delphinus object for the night is NGC 7006, a globular cluster, fainter than 6934, and unresolved at 210x. It appears slightly asymmetric, brighter towards the pair of faint stars adjacent to the south.
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