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Mysterious histograms
Forgive me for reposting some content here rather than the beginners astro forum, but I'm desperate for some advice.
I'm a beginner in astrophotography, using a Canon 70D with a 120mm refractor. My issue is that after taking 30 min of data of M42 (60 x ISO1600 30sec subs), the subs look fine but the RGB histograms lying quite to the left, but after stacking in DSS with darks and bias files, the stacked image is terrible with the dotted line crossing diagonally across the histogram (I'm not sure what it signifies) ie., not a normal sigmoid shape like a wave front.
I've attached screenshots of the camera's RGB histogram of a single unprocessed sub from the camera, and the stacked files with its histogram. The last screen shot is a single sub in detail.
Any pointers would be gratefully accepted.
Luke
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