M71: rich open cluster in Sagitta


RA: 19hrs 53min 48sec   Dec: 18 47' 00"   Mag: 8.3   Distance: 18000 light years   Constellation: Sagitta

My reference books cannot agree on whether to describe M71 as a globular cluster or an open cluster, so I have named it as a compromise between the two.  If the colour detected by my DSI can be trusted, then it shares more characteristics with a globular cluster than an open one with many yellow and orange stars in it.  Compared with deep sky nebulae, star clusters are relatively bright and I didn't have to take many raw images to combine.  This shot was achieved in one run of stacks by Envisage and DSI.

12x30 second images were stacked giving a total exposure time of 6 minutes on the 30th of August 2005.  During histogram stretching, I had to be careful not to extend the white end too much as, although more and more fainter stars became visible, the texture of the background developed an unpleasant over-digitization appearance.  I did very little else to the image other than to pass it through a single run of unsharp mask (75%, radius 1.0, threshold 5).  As you can e in the stars at the lower edge of the photo, there is coma aberration.   I wonder if this photo would look any better if it were passed through a deconvolution algorithm?

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