I recently took some pictures of Andromeda with a SA-GTI and a lumix g85 with the lumix 100-300mm, but the noise of the final image is really bad. Here is the first picture taken with a total of 2.5 hours (315*30s):

With this noise, I thought it was waking noise due to the almost perfect polar alignment. Since I don’t have a dedicated computer and autoguider to dither, I just did it manually by moving the axis of the mount a bit to move the object on the sensor every half hour. For reference, the object stayed within the center cell of the grid of thirds, so I’d say I moved it a few hundred pixels every time in different directions. Here is the result (293*30s):

(Both pictures are processed in siril with green noise removed at the end) The noise stripes are smaller, but there is still a lot of noise in my opinion. It this due to the sort total exposure, or might it be walking noise? How can I reduce the noise without buying new equipment?

  • Thorry@feddit.orgEnglish
    4·
    9 days ago

    I don’t think this is walking noise, that would result more in a blur across the image. This seems like you are pushing the sensor too much and its noise to signal ratio is getting poor. How many darks did you do? And how many light at what settings? I think you should decrease the gain and compensate with longer exposures. However this will increase how much the alignment matters.

    My suggestion would be to bite the bullet and invest in a small guide scope with a cheap sensor. Make sure the guide scope is very fast, that way the sensor can be fast and cheap.

    • Linsensuppe@feddit.orgOPEnglish
      2·
      9 days ago

      I did both of the images with ISO 1600, 30 sec. exposure and F7.1. My camera and lens are able to go to ISO 25000 and F4.9 at the focal length. For the first image I did 50 calibration frames of each darks, biases and flats, and for the second image 30 of each

      I’ve had success with way worse settings. This was taken with ISO 6400 and F6.4: https://lemmy.world/post/25110033 Could it be the difference in exposure? Maybe ~1000 images at 5s is better than just 300 at 30s?

      • Thorry@feddit.orgEnglish
        2·
        9 days ago

        Hmmm yeah it’s probably something internal to the camera that’s not playing nice at 30 secs. Maybe the sensor getting too hot or a noise reduction system which isn’t handling the long exposures.

        Maybe 10 or 15 secs will fair better? Pretty sure the issue is camera noise, not the alignment.