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Rosette Nebula

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Through thin clouds this evening I've had my second go at the Rosette Nebula, and my first go with bias frames. Using Altair IMX224 with 200mm lens at f4 piggybacked on my Nexstar 4se.  I'm super proud of this picture - it only took me an hour or so this evening, and I'm pretty limited with Alt-Az, but slowly improving my technique and I think I'm starting to get some reasonable results - hope you like it too.

60x26s, 24 darks, 100 bias. DSS+GIMP


I found the bias frames do seem to have helped out with a bit of a left-right gradient I was getting before. Interestingly when I shot them with the very shortest shutter speed (0.1ms) the noise pattern seemed very high... so I slightly slowed it to (0.3ms) and found the noise dropped right off. When I tried processing with the 0.1ms and 0.3ms bias frames, I found the 0.1 made the stacked image far worse, whereas 0.3 helped. In summary, when running the IMX224 at very high shutter speeds it looks like maybe it (or the Windows driver??) engages some kind special mode which unfortunately also makes it very noisy. Well, that's a lesson learnt!

Also wished I tried using bias frames before!


NGC2244 DSS 12bit darksMed longBias 26sMed v1_stretched2.png

Edited by Grogfish
Original TIFF didn't upload properly - trying PNG!
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