Saturday, March 28, 2009

Bino Doubles

I cheated a bit and used my ETX-70 instead of binoculars but had fun anyway. I intended to seek out bino doubles in Camelopardalus but it had already sunk below my limited horizon (it was behind the house) and so I had to settle for UMa and UMi instead. I was able to snag 4 of the 5 in UMa, all except Wnc aka M40, and the only one in UMi. I had the devil of a time trying to get the ETX to track right for some reason or other. I finally got it to align ok using a one star alignment on Mizar/Alcor and figured out how to set RA/Dec (again). S 598 was nearly overhead and hard to focus but I was just barely able to split with the 27mm ep. 65 UMa was the first and it split right away with 27mm. Limiting magnitude was about 8 with the ETX, probably 3 or 4 unaided. It was a nice night, cool, humidity about 10%, no wind, clear. Lots of light polution as usual in our backyard observatory. Zeta UMa was nice as usual. Struve1831 showed up nicely in a nearly dark field. Pil in UMi was in a nice little 4 star asterism that kind of looked like a dish antenna pointed at a 4th star. At first I thought the 4th was the double but closer examination with a 10mm ep revealed the double as the top star of the 3 star 'dish' (SAO 2556). It was hard to split even with averted vision. 30" seems to be about as good as the ETX will do.

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