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Hello all, Attached are two images and a screenshot. As you will see, there is a deep red vignetting around the outside. There is also a weird pattern throughout. Can anyone explain what this is and suggestions on how to process these in Pixinsight other than just cropping them out if possible. Light Pollution: Bortal 4/5 Moon 95% Equipment and Integration: Camera: Unmodded Canon SL2 Lens: Rokinon 135 f2 Filter: NiSi Natural Night 77mm Mount: Skywatcher Star Adventurer GTI unguided 170 subs at 40 seconds. Darks, Flats, Biases, all taken during same session.  Drive link: https://drive.google.com/drive/folders/1aNjcED-stSTajJ6FWkZQCqEezoD49DTk?usp=sharing |
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Typical walking pattern noise when your images are not dithered. Try to move the fov a few arc mins every 5 images or so.
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The red vignetting is beacuse your flats might have not worked. Its always a pain to get the flats right in a very lightpolluted location, with poor quality single frames.
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Marc-Antonio Fischer: Would a guider help with dithering with such a wide FOV? |
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Marc-Antonio Fischer: Did I just use the wrong exposure? |
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The wierd pattern is called walking noise and it happens when you have a slow drift in one direction. This is bad because noise reduction won't eliminate it completely. The only way to get rid of it is to do something called dithering. Every few frames you move the telescope randomly by a few pixels. Since you are running unguided the best way to do it is to use NINA and dither using the "On Mount" guider option. On flats, just take sky flats as it's super easy. Just point your setup toward the zenith and shoot a series of frames with exactly the same orientation and filters as you used at night. No flat panel or t-shirt needed, easy! |
