Doubles from Danville

by Mark Wagner

Last night after 11 PM I went out back to my 10" f/5.7 scope and poked around Aquila for double stars. The moon was already past 1st Q and bright, low in the west. The limiting magnitude was probably around 4, at best - the sky looked silvery rather than black. Conditions were about 7 out of 10 for steadiness - there was some scintillation making the stars a bit fuzzed out - squirmy - rarely did I see real pinpoints on the brighter targets, but of course the dim field stars all looked good. I spent about an hour, part of which was sipping a warm beverage - all in all it was a very pleasant experience.

I began with Zeta, a type AO star 83 light years distant at mag 2.99, with a 5 arc second split to its 12th magnitude companion. No dice. The 10 was not going to hit mag 12 in these conditions so close to a bright star. I looked for quite a while, occasionally thought I saw something north of the field's lucida. I think this would be a fun target on a better night.

Next was pi, type F2 and 570 light years away. This was an easy target being very close to Altair and Tarazed. This is a close double, with a separation of only 1.4 arc seconds. It showed some elongation but would not split cleanly. The pair are listed (in the reference I was using - The Seasonal Star Chart) at mag 6.0 and 6.8.

On to 5 Aquilae, type A2 and 259 light year. The pair are mags 5.9 and 7.4 and an easy wide split at 13 arc seconds. I hopped to this target off Lamda Aquilae - my 9x50 finder making it easy. The color was quite nice, the primary being solid white and the dimmer companion a washed out blue - a tinge. A visually pleasing pair.

11 Aquilae is a mag 5.7 and 9.2 pair, type F8 primary, 155 light years distant. Located conveniently just off Zeta and Epsilon, there is a noticeable color difference between the components, with the dimmer member seeming to be even dimmer than the 3.5 magnitude difference. Easy split at 17 arc seconds.

15 Aquilae was, to me, the prettiest of the night's doubles. At the southern tip of the constellation, just off Lambda, it is easy to locate. The primary is a type K1, red, at mag 5.4 and 324 light years. Visually, the primary appeared yellow gold, the latter showing the red nature of the star. The companion though, described in the reference as "lilac" ... to me appeared coppery yellow, and was noticeably dimmer at mag 7.2 with a wide 38 arc minute separation.

After 15 Aquilae, I went on to observe 57 Aquilae, Struve 2446 and Struve 2628. They were fun too, but did not compare 15 Aquilae. It was getting late, and my cup was empty. I was done.

The scope is still out back, where I will continue in a different constellation tonight, with a bigger moon.

Maybe I'll even look at the ..... moon?

Posted on sf-bay-tac Jul 27, 2004 11:03:56 PT
Converted by report.pm 1.2 Jan 04, 2005 22:52:48 PT