Dull colors and grey sky

[Vox45]

Hello all,

I imaged M101 and I am a bit bothered by the dull colors and the greyish sky that results from my processing (in pixinsight) I cannot seem to get a good dark sky and vivid colors on the galaxy.

What do you think ? Any tips to improve ?

 

[MARS1960]

I'm still learning PI but i just quickly ran a 4 instances on your PNG image.

I used a star mask at default then did a high S curve in curves, then a Satuturation curve, i then removed the mask and ran SCNR to get rid of the green.

Not great by any means and some time with tif and the above instances should, with some care give you some colour and darken the background.

I'm sure someone much more knowlegable will be along to show you how to do it properly.

[Vox45]

8 minutes ago, MARS1960 said:

I'm still learning PI but i just quickly ran a 4 instances on your PNG image.

I used a star mask at default then did a high S curve in curves, then a Satuturation curve, i then removed the mask and ran SCNR to get rid of the green.

Not great by any means and some time with tif and the above instances should, with some care give you some colour and darken the background.

I'm sure someone much more knowlegable will be along to show you how to do it properly.

Haaa that means that I can still get more from it ! I never used the star mask and I don't know what SCNR does (Subtractive Chromatic Noise Reduction) ... I still have a LOT to learn Thanks for giving it a shot it looks a lot better and the sky is way darker. I see that the "green" is responsible for the greyish sky right ?

[MARS1960]

I would have a look, a default SCNR alone should improve the colour of the image both fore and background.

I didn't notice at first look but looking again your image is quite green, SCNR is something i always run regardless, if i forget it's soon pointed out when i post an image.

Here is a link you may find helpful.

http://www.lightvortexastronomy.com/tutorials.html

[Vox45]

3 hours ago, MARS1960 said:

I would have a look, a default SCNR alone should improve the colour of the image both fore and background.

I didn't notice at first look but looking again your image is quite green, SCNR is something i always run regardless, if i forget it's soon pointed out when i post an image.

Here is a link you may find helpful.

http://www.lightvortexastronomy.com/tutorials.html

Thank you for the tip !

[Bruce Leeroy]

Reduced noise in a very amateur way using GIMP...duplicate layer, set top layer MODE to "multiply" keeping the lower layer "normal" then slide the opacity slider to desired %, lost some photons in the process.

I used 50% opacity for a dark background.

(optional) I did desaturate the top layer hence the loss of colour.

[Vox45]

After watching a couple of tutorial and putting some more work into it, I came out with this result.

-> using SCNR helped

-> Dynamic Background Extraction (DBE) helped a lot on the greyish/greenish background

-> I noticed that my light frames had some field rotation due to a bad PA but fortunately (I think) that provided a natural dithering so I did not use the Darks this time as I felt they were introducing some defects.

All constructive comments are welcome

[ollypenrice]

I thought your original image had far from a grey sky. The background seemed very 'colour busy' to me, though the galaxy lacked colour - which isn't unusual in raw data. Mars pulled a good deal more colour out of M101 in a convncing way. I process this kind of stuff in Ps so can't advise on how to add colour without noise in PI.

Olly