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Location of Photo:

Julian, CA

Date/Time of photo:

December 4,2021


Planewave CDK24, L600.


So I'm comfortably setup with the PL16803 CCD for a lengthy December galaxy session and my wife says "Do you know about the comet?". We'll, I did not know about the comet. )-: The PL16803 CCD needs at least 5-minute subs for a decent signal and it's too much work to suddenly swap in the ZWO ASI6200MM for 15-second or better subs. So how do you shoot a comet using 5 minute subs? Gotta track on the comet, and the Planewave L600 does that pretty well. With 5 minute subs and pretty good polar alignment, the L600 appeared to track to within 10 pixels (unguided) over 5 minutes – or less than 5" error. I guess that's "OK" for a comet. (-; So here's 30 minutes L and 15 minutes of each R, G and B from 3:30 AM (comet at 21°) to sunrise just after 5 AM. Subs were calibrated and then manually aligned with PI DynamicAlignment. The aligned subs were then combined using PI ImageIntegration, Winsorized Sigma Clipping, Sigma low = Sigma high = 1.000. The star background was shot the next day with the same 5-minute subs during the same 3:30 AM to sunrise with the comet out of frame. Faint star trails were removed with the PS Spot Healing brush. So not perfect, but I'm very happy to capture it without much extra effort.