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Hi, Streaks appear on my photo after stacking my images, all oriented in the same direction. This does not happen every time but, I have the impression that when the signal / noise ratio is lower the final image are more prone to this problem.According to my calibration of my mount on the celestial pole I am a little less than 2 sec of arc from the ideal position. Each 3 min photo seems ok, no streak. I use pixinsight, imagesplus and registar software.So how do you get rid of these streaks with pixinsight software? I tried to increase the number of darks composing the master dark but that does not change anything on the final appearance of the stack.full spectrum Canon T3i cameraAny suggestions? Thank you. Luc |
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| It's very hard to get rid of walking noise after capture. The two best methods for eliminating walking noise are to get your polar alignment 100% right and to use dithering. I don't dither yet, so in cases where I've had walking noise (thanks to bumped mount, for example), I simply gather more data and use kappa sigma clipping when stacking. In the past, that's kept me from having to trash data with walking noise. |
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| What Chris said.Any kind of noise which has a pattern is hard to get rid of. DSLRs are particularly bad. Dithering is by far the best solution, even with good polar alignment. Programming an aggressive random dither every 2-3 frames will make a major improvement. Both SGP and Backyard EOS support dithering. |
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Hello Chris, i've tried dithering once with ByEOS software but it was very time consuming. But perhaps it is a good idea to use it anyway. I will check my polar alignment as you suggest and thanks for the advice for the kappa sigma clipping i will try it. Thanks |
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Hello Arun, Ok so dithering is the solution whatever the polar alignment quality. So I will do it ! thanks, Luc |
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| Yeah, that's the main reason I don't dither. Ever since I got a PoleMaster, I've only experienced it once. I knew I bumped my mount but underestimated how badly I knocked things off. Adding another 4 hours of data got rid of it. |
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Hi, The root cause is pattern noise on the sensor, and the slightest inaccuracy in polar alignment will add the patterns during integration, resulting in the dreaded streaks. I have found that this kind of noise is reduced significantly with good darks (which is not the same as *many* darks, essentially you need to match your sensor temperature while taking the lights). It disappears almost completely (at least in subs taken with my D7500) if I use a Bad Pixel map: https://www.astropixelprocessor.com/community/tutorials-workflows/creating-a-bad-pixel-map/ https://pixinsight.com/doc/tools/DefectMap/DefectMap.html https://rawpedia.rawtherapee.com/Dark-Frame (scroll down to the section "Bad Pixels") I am not sure why. Most likely explanation is BPM interpolation "destroys" the noise pattern, so there is nothing to cause streaks. You still get other artifacts of problematic tracking, such as more elongated stars. Cheers, D. |
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Hi D., ok, interesting i will check the quality of my darks... and the info on web sites you suggest too ! thanks Luc |
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If by streaks you mean vertical or horizontal bands, CanonBandingReduction script works very well, just make sure you apply to to linear image before anything else (before DBE etc) and rotate the image so that your bands are horizontal. Ideally this should be applied to each individual frame, but I found it in my case it works very well on integrated image. Hope this helps Saulius |
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Hello Saulius, this is a different problem than the horizontal or vertical bands. However, I frequently use CanonBandingReduction but after DBE and without proper rotation so, I take note of your suggestions which will be very useful thank you Luc |
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I have a simple way to cover the "walking noise"/"rainwash pattern" , it only cover the noisewith "more" noise but the image will look a bit better. The only solution to walkingnoise is dithering . youcan check my youtube channel for PixInsight: Rain Washpattern removal demo https://www.youtube.com/playlist?list=PL0vHXp9L4HRB1BHOYA6yxDroQzDR14O0T |
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| If you dither and use drizzle integration it should go away. |
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You must be very good with polar alignment at 2 seconds error. I don't see this type of noise and my polar alignment is usually 1 to 3 minutes error. I doubt your noise is due to polar alignment at 2 seconds error. Alignment at zero, is impossible. |
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Hello Rich Sky, Perhaps it's only poor seeing after all.... Thank you |
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| Startools has an excellent module called heal which is brilliant for ridding artefacts, time consuming if you have loads but you’ll never know it was there , I dither between frames using APT , so only take flats , bias frames I have a library so in Siril I use no dark script so I only need lights flats and bias frames . |
