Re-processing my data from M31 using M101 image to create sky background to subtract from M31 image to remove light pollution

Follows on from:

Re-processing my image of M31 from 26/8/2019 today 27/8/2019

I used M101 image from a previous night to create sky background image to subtract.

I created 2nd layer and slightly shifted it to make starts more round in shape.

I used curves to bring out data.

I used clone tool to clone out black spots that appeared in image after processing with other methods above.

I used Ian’s noise reduction in G’MIC plug-in for GIMP.

……Uncertain whether I prefer this image to previous versions!


Images below show different amounts of above processing:

2 Responses

  1. Hmm!
    Yes, you can overdo the Ians noise reduction!
    I sometimes use “Selective Gaussian Blur” (In the standard filters, not in Gmic) that has a similar effect but not so harsh.
    Also rather than “Clone” for editing out spots, you might find the “Repair” tool better. It works in a similar way.

    1. Hi Roger
      Thanks for your comments and for all of your advice and for spending lots of time with me at RAG last night helping me improve my processing techniques.
      I do agree that your PD images are amazing considering the simple equipment and ease of use and yes I must try that out too.
      Please take a look at my latest post on the blog where I have used Nebulosity to process the M31 data. In face the data Nebulosity used was 8 x 1 min exposures that I also took the same evening and discarded because neither Registax, Astrostakkart or Deep Sky Stacker would acknowledge there was any data in the images to stack. Nebulosity took them in its stride and the resulting photo is a lot nicer than my other attempts in my view. But what do you think?

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