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PostPosted: Sun Aug 02, 2009 12:01 pm 
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Location: Brockenhurst, Hampshire, U.K.
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O.K. so not aliens trying to signal us by modifying a star's output (mind you that isn't a bad idea) - but actually a very variable, variable star called WY Cassiopeia near the open cluster NGC7789. This is an animation of two images taken 6 months apart showing the enormous change in brightness magnitude in this star over just 6 months. And yes I did think it was something a lot more exotic than a variable star when I first saw it. Digital image processing as usual by Noel Carboni, image acquisition by Greg Parker at the New Forest Observatory.

Greg

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http://www.newforestobservatory.com/
http://www.flickr.com/photos/12801949@N02/


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PostPosted: Sun Aug 02, 2009 2:27 pm 
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Hi Greg,

Who needs blink comparators when ANI GIFs are available? We can now play "spot the variables" in your image. Most obvious are the two in the upper left quadrant, one being very close to a brighter white star. Binary or an optical double? I'm guessing the latter because it's brighter and that's hard to square with a dimmer red giant of the same age but my introductory astrophysics is fading in memory, somewhat.

Bob.

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PostPosted: Sun Aug 02, 2009 2:33 pm 
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Location: Brockenhurst, Hampshire, U.K.
Hi Bob,

Yes you are right - but you have to be a bit careful. These two images were taken with two different telescopes with two completely different fields of view, and Noel had to do quite a bit of size/brightness manipulation to get the 2-images looking at all similar. If you look carefully there are a number of stars that look "slightly" variable - but it's just the processing. The only true clear candidate here is WY Cass - and that one is unmistakeable :D

Greg

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Nexstar 11 GPS, 2 x Sky 90, M25C, MaximDL, Photshop CS3, Noel Carboni's Photoshop actions, 7 foot Pulsar fibreglass dome, Canon 40D, 100mm macro lens, 28-200mm zoom lens, 17-55mm f#2.8 zoom lens, 100-400mm zoom lens, 1.4x converter, 2x converter.
http://www.newforestobservatory.com/
http://www.flickr.com/photos/12801949@N02/


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