Sunday, December 10, 2017

IDed (a) double(s)

I learned (using the Washington Double Star database) that the bright pale orange star at the top-left corner of the M25 image, i.e. north-east from the centre of the open cluster Messier 25, is double star ARN 52.

It consists of a pair (only) with A at magnitude 7 and the secondary around mag 10. They are separated by 69 seconds of arc. The position angle of B is 262°. B is white.

SkyTools 3 Pro shows these stars as HD 170886 and TYC 06275-0740 1 respectively. The magnitudes match. The position information matches too.

Then B appears to have a tight deep red companion! Interesting.


Oop. Encountering more stuff.

The relatively bright star below BU 966 C is D, according to the WDS. Slightly brighter than Q. Almost due south of C. Close to C. Off-white. The D star is not listed in ST3P.


The WDS shows ARN 107 in the area. A simple pair, with magnitudes 9.7 and 10.9. The quoted PA is 289; sep. 21.2. This is nearly due south of BU 966 C (and D), east of the bright orange star TYC 06274-1625 1. The A star is white; B is grey. ST3P does not note this double; the individual stars are TYC 06274-1251 1 and TYC 06274-1349 1.


I noticed this in the August image but didn't dig deeper at the time. All white-grey stars. South-east of ARA 753 a very tight pair. The bright element is between the magnitude of 753 A and B. The position angle is around 135°. The stars are touching. So they are probably have a separation around 4". This extremely tight pair is to the north-north-west of a medium-bright star. This star shows in SkyTools as TYC 06274-1650 1 at mag 11. But the pair is not shown in the software!

The WDS refers to ARA 752. 752 is a pair, mag 11.0 and 11.6, PA 284, sep. 10.9. The angle is very different. The gap between the tight pair and the Tycho star looks double the ARA 753 sep. So, is this it? It's a little confusing.

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