Telescope: Celestron C9.25 @ f/10, Orion Atlas EQ-G
Camera: QHY 168c, -10C
Filter: Orion Imaging Skyglow Filter
Guide scope: Astro-Tech 60mm, ASI290MM Mini, PHD2
Exposure: 104x30sec saved as TIFFs
Darks: 32x30sec saved as TIFFs
Flats: 32×0.050sec, tee shirt flats taken at dusk
Average Light Pollution: Red zone, poor transparency, bright moonlight, clouds
Lensed Sky Quality Meter: 17.0 mag/arc-sec^2
Stacking: Mean with a 2-sigma clip.
White Balance: Nebulosity Automatic
Software: Nebulosity, Deep Sky Stacker, Photoshop
This is M13, the Great Cluster in Hercules. If you look carefully at M13 you can see a dust lane to the lower left of the cluster. This is a very unusual feature for a globular cluster and it is not clear if this is actually associated with M13 or simply lies in our line of sight.
This is one of 5 images that I took under fairly poor conditions to evaluate my C9.25 for deepsky imaging in its native f/10 focal length. Although not as good as a modern Edge or ACF Schmidt Cassegrain, it does fairly well with an APS-c sensor.
M13 is currently well placed, high in the northeast after sunset
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