Asellus Tertius or Kappa Bootis

[mike.brightmore]

I was intrigued by Steve Richards description of this double in the May Sky@Night magazine (Deep Sky Tour) in which he states that the brighter star of the pair (mag +4.5) is bright yellow and its fainter companion (mag +6.7) is blue. He also says that 'you may also see the colours swapped around'. Having never seen it before I thought I'd take a look last night and to me the larger brighter star had a distinct blue tint and the smaller one white. The colour distinction became more pronounced when slightly de-focussing the stars. The photo below does show some blue in Kappa which I don't think is CA. Seen better if enlarged. So why does the colouration appear different to different observers?

[John]

Interesting Mike - I've not viewed that one for a while so I'll take a look at the next opportunity and see how they look to me.

I'll report back .....