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Sigma Cas.


Paul M

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Having set my scope up last nigh (Sky Watcher 250 P DS EQ6) mainly to get another look at Comet Jacques I was struggling with light pollution.

Under whelmed by the comet (nothing wrong with the comet, just my bright sky) I pressed the "tour" button on the SynScan handset. Many of the objects suggested were fuzzies which my sky wasn't too good for. So I found the Double Stars sub-menu.

I'm not an avid double star observer and I'd already had a peek at Alberio after reading a thread the other day about observers struggling to see colour in its components.

I was relieved to find that I still could. Although not as vivid as when I was a young boy under dark skies!

SynScan offered various choices and gives some info too. Many of them were quite wide and I wanted a challenge having not tested this scope with resolution challenges,

Sigma Cassiopeiae sounded interesting: mag 5 and 7.1 with only 3.1 arc seconds between them.

I told GOTO to go to and it went.

I had my 28mm eyepiece in at this point giving me about 42x magnification. I didn't expect to separate it with that and certainly couldn't. A quick look on SkySafari helped identify the field stars and center the correct one. In went my olde 12.5mm Ortho  giving me 96x. 

This easily split them. Easier than expected. I couldn't discern any colour contrast. Both component were white to me.

Just to push things further I popped in my ancient 2x Barlow giving me 192x  . I was concerned to see that both components were slightly elongated :( 

As chance would have it the elongation was on an axis perpendicular to the line separating the components. There was yards of clear sky between them still.

I decided that collimation needs a look at but was surprised it was so obvious at under 200x given that it's fine at lower magnifications. Not to worry though, I'd had pleasing views of a new double for me and one which is noted by some reports as being challenging.

When I finished my session last night I just moved everything into the kitchen for putting away properly in daylight. 

So this morning I was sorting through and found I'd left the eyepiece in the Barlow. It wasn't the 12.5mm Ortho I was sure I'd put in but a 6mm Plossl. This mistake came about because I'd put them away in the wrong boxes last time.

More to the point it means my observations were made at 200x and 400x !

I don't feel so bad about that star smearing now, although I will have a look at the collimation just to be sure.

Anyway, perhaps 400x is a bit much for a f4.7 newt ? :)

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35 CAS is another double in Cassiopeia that worth looking at. Lovely contrast red and white.

Thanks, I'll give that a bash next time I'm out.

At least double star observing isn't as troubled by sky glow as Deep Sky obs.

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Eta Cass is a favourite of mine but I suggest also look at the nearby Cepheus with Xi and Delta both worth finding (and of course the Garnet Star ... because it is there). Like you I am still surprised at how much magnification some doubles can take.

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