M71: rich open cluster in Sagitta
RA: 19hrs 53min 48sec Dec: 18º 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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