29/30/31st March 2021

So three(ish) nights of fairly clear skies with fairly good seeing finally. Pity the moon was waxing but we can’t have everything.

Skywatcher 200PDS, HEQ5 - Guided. 600x 42 / 300 x 50 / 180 x 20 subs. Total exp. 12 2/3 hrs

So I had quite a lot of light for this shot of M81 and M82. Some of it was fairly light polluted though and there was some high cloud in some but I though I’d see what I could make of it by just dumping the whole lot into Astro Pixel Processor. I think it’s done a reasonable job but I did initially end up with a fairly blotchy background.

(Skywatcher 200PDS, HEQ5 – Guided. 600x 42 / 300 x 50 / 180 x 20 subs. Total exp. 12 2/3 hrs)

I used the APP light pollution tool on the complete stack and then used PixInsight to stretch and process it. My workflow looked something like:

  1. MultiscaleLinearTransform to do some noise reduction
  2. Stretch
  3. MultiscaleMeridianTransform to reduce the blotchy background
  4. HistogramTransform to reset the blackpoint
  5. HDRMultiscaleTransform to bring out some detail

I had quite a lot of trouble with step 5. The enhancement worked fine in the preview but went weird for the whole frame. In the end I made two previews of the galaxies, did the transform, saved both the images then merged them into the final image using GIMP.

I’m quite pleased with the first result but I was a bit bugged by the blotchy background so I went through the raw data by hand and filtered out the cloud polluted frames. This cut out about 3 hrs of light.

(Skywatcher 200PDS, HEQ5 – Guided. 600x 34 / 300 x 34 / 180 x 20 subs. Total exp. 9 1/2 hrs (Selected data))

The background did indeed come out a lot better so step 3 wasn’t needed and step 5 worked on the whole frame but on the whole I like the first attempt better.

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