02 May 2010

Doubles hunter

With my brand-spanking new Double Star Atlas, I can now really and truly have a go at hunting doubles!

Last night was the first in ages that was actually clear. There were some high wispy clouds at sunset that had J panicking, but they went away so we went outside. As well as my Atlas, the other exciting new thing I have is a Cat's Perch! J's been talking about getting a star chair for months, and he ended up ordering two of these - it's so much easier to focus and hold steady when you're sitting down, rather than standing. He'd constructed them last weekend, and sanded them yesterday, so they were ready for a test. And I loved mine: I was observing to the west, so I ended up having the scope very low down and the seat correspondingly so. I could have had it higher, but I think that would have been more annoying.

So, what did we see? I started off with Saturn, of course; and it was lovely. I could definitely see the shadow band under the rings, and I could just see one moon, which was either Rhea or Dione. I then swung around and decided to play around in Canis Major, to see what doubles I could find and whether the Atlas is going to work for me.

Firstly, I'm glad it's spiral-bound. The Atlas has 30 double-page maps, with constellations and doubles and some other features marked. Then, at the back, it has the list that the authors worked from, of which doubles to include: this has the magnitudes and separations of the respective stars. This is very, very useful when you think you've found the right star, but you're not sure you can see a companion, so you need to know whether they're only 8 arc-seconds apart and therefore unlikely to resolve under light-polluted skies (which happened to me), or whether the companion is TWO HUNDRED AND SIXTY FIVE arc-seconds away and therefore could be one of three faint stars you can see (I am annotating the list as I go, with ticks and dates of when observed. This one I also annotated with "srsly?!"). The one problem - and this is only a problem for me, not the book - is that they're in right-ascension order. This has to do with how the stars are mapped, and I am struggling to really get my head around it. (Dumb moment of the night: realising that I was treating the lines of right ascension and declination as if they were straight, rather than curved....) This is something that I will get used to over time. I presume.

Anyway. Canis Major. Start with Sirius; no luck splitting. Move up to Wezen: success! (At least, I presume so; that's the 265" split.) No luck with Adhara (7" split, so not that surprising). Then, on to some harder ones. There's a little group of three along the 'spine' of Canis, two of which are noted as binaries. I hazarded a guess at where they should be, looked in the scope... and didn't think I'd found it. Asked J for some help, tearing him away from his open-cluster hunting, showed him the map... and he found exactly the same thing. I looked at it a bit longer - checked the list at the back - and realised that actually, one was a triplet, and that's what I'd been confused by: the top star in my eyepiece had two very faint stars nearby, which was indeed my triplet! This was also helpful because I now have an idea of what 44" looks like. That was 17CMA; sadly couldn't split pi, so that will have to wait for another night. After that success, I attempted tau-CMA, which is in the open cluster NGC 2362 - which, I didn't realise, is J's favourite little one. And I found it, and I think I saw the double; at 85" separation, in a cluster, it's hard to be positive.

Unfortunately, I didn't have a great end to the night. There's another little group of three, between Sirius and Mirzam, that looked like they should be easy enough to find - two are bright-ish, and they're convenient between those two very bright stars. I got quite frustrated because I just couldn't find them. So J had a go, and swapped in our widest eye-piece. Turns out I was looking in exactly the right place... but I had totally underestimated just how wide the set was. This is another thing I will have to get used to judging. Anyway: I split v-1CMA and v-3CMA (although the latter doesn't appear to be in the master list, which is odd).

The other thing I have to get used to, and adjust my expectations for, is how many things I will manage to see in a night. At the moment, the answer is not that many. J has much more practice with observing, and reading charts, and is not handicapped with a monumentally unspatial brain like me - so he's always going to see more. It's also a lot easier to tell when you've hit a cluster, than when you've hit a double, so he can skip around more easily if he wants to. I think this is something I can deal with... eventually... and as I keep reminding myself, the sky actually will stay basically the same for my entire life. It's not like I'm running out of time to do this.

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