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M55 through haze


MarkS

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A hazy and cirrus-strewn sky forced me to target a Globular Cluster, as this was, I thought, the best chance of a result.

 

M55 has very low metallicity - it's very old, even for a GC - but it also has an unusual number of 'blue stragglers', apparently the result of relatively recent star mergers and collisions.

 

In the event, I got about 3.5 hours RGB - all 2.5 minute subs to minimise star saturation. Half of the blue subs were unfortunately very heavily contaminated with scatter through cloud, so some clean-up was necessary. Otherwise there is only a little decon to sharpen things a bit, background neutralisation, and photometric colour calibration in Pixinsight, followed by a simple histogram stretch.

 

ASA10N at f/3.6; DDM85A; G3-16200; Astrodon filter set.  Field of view 32' x 25'.

M55.jpg

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