13 Vul - WDS 19535+2405 - Anyone?
Posted 17 August 2013 - 05:28 PM
Anyone else tried this one recently?
Posted 17 August 2013 - 11:56 PM
Posted 18 August 2013 - 03:35 AM
Posted 18 August 2013 - 10:17 AM
Posted 18 August 2013 - 02:55 PM
Posted 26 August 2013 - 08:46 PM
13 Vul is missing from a lot of double star listings - including the Haas book, unfortunately. It doesn't appear in the older observing guides because it was not discovered until 1953. The measures since that time show a nearly linear increasing separation since that time - have a look at the orbit diagram, which plots the measures as well, in the 6th Orbit Catalog. It's in the Orbit Catalog because some brave soul has made a first attempt at calculating the orbit.
If we go backwards, before 1953, it's obvious the likely path takes the companion VERY close to the primary star - perhaps around the time when Robert Aitken, at the beginning of the 20th century, was systematically surveying the northern sky for new doubles. So it might have been missed then because it was simply too close at the time. The discovery separation was 0.8", compared to 1.4" in 2009; it could have been as close as 0.1" in the beginning of the 20th century, as suggested by the orbit diagram.
The 1953 discovery of 13 Vul as a double was due to a post-WWII double star program at Belgrade Observatory, which had a 65cm Zeiss refractor. This discovery was part of the first of a continuing series of double star studies undertaken there.
Looking at the orbit diagram, the suggestion is that this pair will soon reach maximum separation, then begin to slowly close again. We'll have to wait and see if this happens - an orbit calculated on such a modest part of a complete ellipse, and without measures yet for periastron or apoastron, is decidedly "preliminary". Likewise the orbital period of 615 years is something of a guess (it fits the calculation, but that calculation is pretty uncertain).
For now, we have another rather nice pair to observe. It'll be interesting to find out what size of scope is needed to see it split. Roberto's reported on his view with a 6-inch refractor; it might prove more difficult in a C6 or similar due to the delta-m (2.74 mags according to WDS) and the secondary star being close to the first diffraction ring, enhanced with a large CO.
Refractors? - I'm going to try it with my 140mm, I've not looked at it with that one previously. Perhaps someone would like to try claiming it with 100mm or thereabouts?
Posted 27 August 2013 - 03:43 AM
Many thanks again for the historical background. The chart on Stelle Doppie plotting observations does indeed show what a limited portion of the orbit has been recorded.
I split this one again on Sunday evening (easier than 99 Her but still close) and noticed a definite blue hue to the secondary. It also looked "fuzzy" when compared to the primary which was a much well defined disc. I remark on its "fuzziness" as after observing other (wider) doubles with a similar magnitude companions, this is one of the few where I have noticed this "structure".
Same setup as for 99 Her was used; "binoviewed" with 12.5mm orthos at 290x and 6" refractor.
Posted 27 August 2013 - 07:10 AM
Many thanks for your very intressting data and history regarding 13 Vul. Not discovered until 1953,amazing. I was born -52 :o
I will try 13 as soon as possible.
All the best!
Posted 27 August 2013 - 07:19 AM
Posted 27 August 2013 - 08:48 PM
Thanks Roberto for guiding me to this nasty devil
All the best,
PS By the way, 16 was a clean split this night at 411X!
8"f/6 OOUK Newt
Posted 28 August 2013 - 06:52 AM
Posted 28 August 2013 - 08:14 PM
I was out this night as well. A bit hazy and dripping wet but indeed great seeing. Stumbling near 10/10 P.
My suspected split from yesterday was defenitely confirmed with my C8 tonight at 411X and 480X. The tiny secondary was also glimsed at 320X. At close inspection the "PA" was sort of WWWS. When I use my CG-5GT mount again with tracking it will be more easy to observe this, for me, rather difficoult double.-A bit of a pain to track with alt-az slow-mow controlls above 400X!
Tonight I also had a look at zeta Hercules. Split at 411X, secondary almost due S. relativ the primary. Looked a bit like Delta Cyg. but notably tighter and the colours were yellowish.
All the best,
8"f/6 OOUK Newt.
Posted 29 August 2013 - 06:31 PM
Posted 05 September 2013 - 06:32 AM
Also visited 16 Vul as per Magnus' post above. Got a nice touching pair of white discs separated momentarily by a thin black line. Diffraction rings for both components.
Posted 05 September 2013 - 08:35 PM
Posted 01 October 2013 - 01:05 PM