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Xi Bootes in Little Cygnus
On the evening of May 9th 2008 Leo and I got together to observe a series of double stars in Bootes, inspired by an article in June's Sky and telescope (Binaries in your Bootes). In the period between the beginning of May and the end of July it doesn't get really dark at night, but for observing double stars or asterisms, this proved to be not a problem at all. We started at 23.00 hours local time (UT + 2hrs). In three hours time we observed and sketched about six doubles in Bootes and two asterisms, one in Bootes (Picot 1), the other in Ursa Major (Ferrero 6).

The highlight for me that night was Xi Bootes. This colorful double lies about 8 degrees east of Arcturus. The Yellow primary star shines at magnitude 4.8 and it's magnitude 7.6 orange companion lies at a position angle of 315°. The separation is 6.3". Through the 17mm Nagler the double looks fairly close (scale from "Double Stars for small Telescopes" by Sissy Haas). When looking at Xi Bootes through the 17mm Nagler, the double seems to be part of an asterism that looks like the constellation Cygnus, only much smaller. Xi Bootes is placed at the position of Deneb, the tail of the swan. We decided to call the asterism "Little Cygnus". On the sketch below the asterism is oriented West-East. At the tail you find Xi Bootes. Three white stars oriented north-south represent the wings of the little swan. A white star to the east (accompanied by a dimmer companion) is at the position of the head of the swan. The yellow star to the eastern edge of the field of view is just a bright field star. It is no part of the "Little Cygnus" asterism.


The sketch of "Little Cygnus " and Xi Bootes was made using the 300mm f/5.3 Dobson and a 17mm Type4 Nagler. The magnification is 94x and the field of view is 52'. At the telescope I made a sketch on white paper using a HB led-pencil. This sketch was scanned and processed in Photoshop. I colored the double star (and the field star to the east) using the tutorial described on the website of Jeremy Perez ( ). This is the first time I experimented with this technique, and I am very pleased with the result. It produces a realistic image and resembles what you see through the eyepiece. In the future I will try to use this technique for sketching more double and multiple stars.

Posted by Math on 06/05 at 09:42 PM
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