by Robert Leyland
| Observer | Robert Leyland |
|---|---|
| Date | 13 July 2002 |
| Time | 2200-0130 PDT (UT -7, or 0500-0830 14 Jul 2002 UT) |
| Location | Lake Sonoma CA, 38°43'N 123°02'W Elev ~1400 (Lone Rock Flat) |
| Weather | 21°C Temp, 44% Humidity |
| Seeing | LM 6+, transparency 8/10, steadiness 9/10 |
| Moon | early first quarter moon (set by 11pm) |
| Equipment | 17.5" F5 Dob, 5" F5 Newtonian, 9x50 finder scope, Pentax XL EPs |
A nice still evening, with a group of 8 or so telescopes gathered. It's early first quarter, with the moon setting around 11pm, while astronomical twilight doesn't end until 10:30pm. Early evening views of the Moon and a half phase Venus were quite steady.
My plan for the evening is to start on a "new" constellation, and work through it using NSOG and SA 2000 as guides. I picked Aquila, as it is well placed, and right at the front of the book :-)
Starting near Altair is NGC 6828, a pretty dull open cluster, about 30 or more stars visible in the 17" (at 100x), but its better in the 5" (at low power 25x) with a wider field of view to give the cluster better contrast with the surrounding milky way. It still seems a bit boring, without interesting patterns, or star colours.
Soon after starting, Linda Mahon offers us a distraction, in the form of the "Fairy ring" asterism in Cygnus. This is a circle of double stars, aligned like spokes of a wheel, so there appear to be two concentric rings of stars. Several pairs have pretty color contrasts, giving the ring a magical quality. Also in the center of the ring is a widely spaced double or golden orange stars. This asterism is great in both the 17 and the 5" telescopes, well worth checking out.
Back to Aquila and a planetary nebula, NGC 6804, which is nice, and bright. Situated between two moderately bright stars (useful for focusing), just above Mu Aql. At 100x a second pair of stars bracket the PN at right angles to the inner pair . Some structure is evident at 160x with an OIII filter. At 320x unfiltered I think I can see a central star, and at 425x (Pentax 5.2mm) detail is excellent (its a very good night for observing), and small arc of three faint stars shows across the face. Returning to more modest powers, some wispiness shows in rings around the PN body.
Bouyed with that success, its off to NGC 6803, another PN. Adjacent to a moderately bright star, it shows as a faint stellar object. Blinking with an OIII filter (as per NSOG), and it brightens up relative to the background. Pull the filter out, and it dims back down.
Now for a trickier planetary, PK 47-4.1, this one is faint and large, just a big fuzzy region, even with an OIII filter. Too faint for any details.
While star hopping around in the area I am struck by the "dark areas". In the past I haven't given much thought (or observing time) to "dark nebula", but these are so obvious, particularly at low power in the 5" it is hard to bypass them.
B 142 & 143 show as a pair of dark splotches at the edge of the milky way field. One (B-143) is somewhat 'C' shaped. In the 17" they are both cool, the larger filling the field of my 40mm eyepiece, and I can't see them both in the same FOV. In the 5" they are very clear, and dark.
The other dark Nebulae B 334, 336 and 337, are not as pronounced, or large. Projecting out from gamma Aql, past B142/143 they fill the field of the 40mm Pentax.
Linda offered up another sidetrack, she's very good at that! This time the object is the "Distant Duck" galaxy/cluster pair in Cepheus. These proved to be an easy find in the 5", both are in the same FOV. At 100x in the 17" the galaxy appears comma shaped, and the cluster has arrow shaped lines of stars.
Returning to Aquila, to open cluster country. Firstly NGC 6837, N of Altair, is a loose open cluster with several groups of three stars in small triangles and lines. Then at the edge of the Milky Way are 6840 and 6843, a bit further afield, These appear to be a couple of denser patches of stars, overall not very interesting.
Then NGC 6858 is another open cluster, larger than the previous clusters and easy to spot in the 5" scope, with a zig-zag line of stars
Planetary nebula NGC 6852 shows as a fuzzy disc with a faint neighboring star. It is an easy find, between Altair and Theta Aquila (near Eta Aql). At 160x the adjacent star is more obvious, and an OIII filter shows a darkening in the centers. Using averted vision the PN looks to have a ring like shape.
Right next to Delta Aql, is NGC 6795, an open cluster consisting of a bright pair of stars with many faint surrounding stars in loops leading away from the central pair, along with a chain of stars leading back towards delta.
Finally for the evening, an pair of open clusters NGC 6755 and 6756. The former 6755 is larger and has 5 or 6 clumps of stars within its totality of around 100 stars. 6756 is a single clump, somewhat rectangular in shape, with a cloud of stars surrounding it.