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Hello everyone, i get a strange pattern in the background of my final stack. I used a ZWO ASI 183 MC Pro at -20°C, gain 50, 30s per shot, 1800 shots in total. Dithered every few shots, blinked through all images, nothing obvious. Flats, darks and dark flats, all in WBPP. The individual images all look normal, even the master flat and master dark are completely normal. does anyone have any idea what the problem could be?  |
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No promises, but I've had similar issues before. Try stacking without your bias frames and see what happens.
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This can also happen if you're drizzling the data with not enough sub exposures or insufficient dither settings. Drizzle works of a weighting map, and if you don't have enough subs you get better weights in some areas than you do in others, resulting in a mesh pattern appearing throughout the image. If it was a calibration issue, you should see it on the images in the 'calibrated' folder that is output from WBPP. If you're not seeing it on individual calibrated subs (though it will be harder to notice)… |
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Hi, Thanks for your suggestions. In the meantime I tried different ways and also made another observation. Blue Smith: Unfortunately this did not do the trick. I also tried to only stack different smaller subsets, with the same result Alex Nicholas: Also this idea did not work out unfortunately. I tried to stack without drizzling, with the same result. And there were absolutely no signs of this pattern in any of the calibration frames. I tried stretching them very much and still no sign. I have about 1800 subs, so this should be sufficient amount. What I tried next: I took the data over a total of five nights and photographed a different object in the second half of each night. So now I tried to stack the data from the second object with the same master calibration frames. The result: no visible pattern. I'm really at a loose end. I can't see any recurring pattern in the individual calibrated raw images either. |
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 I have the same issue, with Canon 600D DSLR  |
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Konrad Krebs: I think its a calibration issue. I didn't have this before but try different combination of calibration settings also check your calibration frames. CS! |
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Yours is different from his. In your case it is walking noise, so the best cure for you is to dither (say 10 pixels) every now and then.
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