First attempt with Esprit 80 ED+ASI 1600mm and processing in Pixelinsight

[Viktiste]

My first ever half serious attempt at anything (M31) with the newly bought Esprit 80 ED+ASI 1600mm and processing in Pixelinsight.

20 x 120s L, 20 x 120s Ha, 10 x 120s R+G+B, Bortle sky "city center". Endless hours of Pixelinsight YouTube tutorials. 

 

Edited November 12, 2019 by Viktiste

[Viktiste]

There are color gradients I just cant seem to get rid of. This is the RGB combination. Any idea if this due to light pollution, poor flats or something else?

[Jbro1985]

Looks like probably LP to me.  There's some good tutorials on LightVortexAcademy that may help if you've not been there.

[Jbro1985]

I used to have similar issues under the city sky.  Switched to Narrowband pretty swiftly but obviously Galaxy hunting is not the best in Narrowband so you need to adjust your mindset towards nebulae too if you can.

[david_taurus83]

Have you tried DBE?

[Viktiste]

Thanks for the comments, good to hear it's likely light pollution and not something with the equipement.

Yes, I used DynamicBackgroundExtraction. I does get rid of some of it. 

I have Narrowband filters, so I will eventually look into that. But for now I'll try to get some more experience with LRGB. 

 

 

[windjammer]

Hi - I think thats quite a good result for M31 esp, if a first go at it !  I have similar issues with simple RGB overlay - weird gradients and patches of unphysical colour.  For me, I concluded it was because I processed each colour filter separately, processing each colour as far as it would go as a monochrome.  So the different colours became uncoupled from each other.  I use Photoshop Elements for the tarting up after the serious stretching elsewhere -PSE is only 8 bit.  My most recent recipe for making the separate RGBs congruent as follows (in PSE speak, but hopefully you will get the drift):

Pick one colour (obviously all the colours are monochrome images at the moment) as the reference, say G.  Compute the flat F(R-G) ie. Green overlay with Red with blend mode 'difference'.  Blur the difference using 'Dust & Scratch removal' at maximum settings.  This removes fine detail from the difference and just leaves the broad wash of intensity differences across the frame.  

Then compute R(new) = R - F(R-G) ie. overlay the Red with the above flat with blend mode difference.  If you get a bit twitchy about this, you can vary the opacity of the flat to vary the volume of the adjustment.

Do the same with B, and compute flat F(B-G) and proceed to create B(new).

Construct the colour composite (Rnew, G, Bnew).  For any major colour tinge remaining, adjust the hue to be pleasing.  For me, green is the most common overall tinge which I adjust to a sun yellow, or a red adjust to a gold.

For any small non-physical colour patches, adjust the hue in either saturation (make it more colourful if it brings up physical detail or decrease to damp it down) or increase intensity (pushing it to a more harmless simple luminosity).

So this is what I made of M31 from an outing mid October...

https://www.flickr.com/photos/31131978@N00/49053267023/in/photostream/lightbox/

Simon

 

 

[adoldesa]

Are you doing flats for each filter? I had problems with gradients when my flats were not correctly taken at 50% of the histogram. However, even then light pollution still leaves some residual gradients, I usually remove it in APP which has a good tool for it. Another problem could be focussing when changing filters, some filter combinations are not parfocal and you will need to re-focus with each one, if this is not done the illumination will not be even across the filters and may produce gradients and strange effects after stacking.

[Viktiste]

I did flats for each filter yes. But I did not re-focus between filters. Learning as I go along. Played around in PI, following some of the suggestions I got. Not great, but a little better:

 

Edited November 17, 2019 by Viktiste

[Viktiste]

That's an unbelievable 45GB on the disc including all the trial/errors and intermediate steps. I guess I need to be selective in what to keep.