Colour Module - Unexpected behaviour

Questions and answers about processing in StarTools and how to accomplish certain tasks.

Colour Module - Unexpected behaviour

Postby midnight_lightning » Sun Oct 14, 2018 11:43 am

Hi,

I have an image of M31 and want to boost the colours within the galaxy without changing the colour of the stars in the image.
I feel I should be able to do this using star masks but I seem to get inconsistent results, can anyone help?

I am starting with my standard process which is :
Enter Colour Module
Set Star mask
Sample
Clear and Invert Mask, Keep

This gives me a good starting point of colour in both M31 and the stars.

If I now go back into Mask and create / keep an Inverted star mask I can use, for example, Saturation to change M31 without affecting the stars - all good.

However, I now want to go back and adjust just the stars. I go back into Mask and Invert/Keep the mask again (so we are back to a Star Mask), but when I get back into Colour after keeping the Mask only the stars still have colour, M31 is grey. Why is this happening, I wouldn't expect just changing the mask to have any effect until I changed one of the colour settings?

For information, this was all done without exiting the Colour Module at any point.

Thanks

Jon


I now
midnight_lightning
 
Posts: 40
Joined: Sun Jul 31, 2016 3:01 pm

Re: Colour Module - Unexpected behaviour

Postby almcl » Sun Oct 14, 2018 9:36 pm

Not sure quite how well this will work with a large target like M31, but there's a technique for separating the stars and background, working on them separately and then recombining, here:

http://forum.startools.org/viewtopic.php?f=7&t=244
Skywatcher 200P with an astro modded Canon 700d, cls ccd filter, field flattener, guided by QHY 5Lm, PHD2
almcl
 
Posts: 83
Joined: Wed Jan 21, 2015 7:15 pm
Location: Shropshire. UK

Re: Colour Module - Unexpected behaviour

Postby admin » Wed Oct 17, 2018 12:17 am

You could post-process the stars after switching Tracking off. That said, you seem to have a bigger problem - a single color balance should work for the entire image, including stars. If it doesn't, something is wrong with the dataset... :think:

If you don't mind me asking, what is the reason you want a separate color treatment for the stars and the rest of the image?
Ivo Jager
StarTools creator and astronomy enthusiast
User avatar
admin
Site Admin
 
Posts: 1725
Joined: Thu Dec 02, 2010 10:51 pm
Location: Melbourne

Re: Colour Module - Unexpected behaviour

Postby midnight_lightning » Wed Oct 17, 2018 10:01 am

Thanks almacl, I will look at that.

The single colour balance was ok with ST but I wanted to bring more warmth to M31 without getting bright red rings around the stars.

I managed to get what I wanted with a bit of post processing using Affinity, see image, but was trying to find a way of doing this in ST.
Unfortunately I didn't keep the original ST image but in order to get the level of yellows shown in this image the stars had quite red rings around them.

Perhaps I'm trying to put more colour into M31 than is really there but I felt it still looked natural (?)
Attachments
M31 APP ST v4 Star Reduction Final 1024.jpg
M31 APP ST v4 Star Reduction Final 1024.jpg (451.25 KiB) Viewed 110 times
midnight_lightning
 
Posts: 40
Joined: Sun Jul 31, 2016 3:01 pm

Re: Colour Module - Unexpected behaviour

Postby admin » Fri Oct 19, 2018 12:22 am

midnight_lightning wrote:Thanks almacl, I will look at that.

The single colour balance was ok with ST but I wanted to bring more warmth to M31 without getting bright red rings around the stars.

I managed to get what I wanted with a bit of post processing using Affinity, see image, but was trying to find a way of doing this in ST.
Unfortunately I didn't keep the original ST image but in order to get the level of yellows shown in this image the stars had quite red rings around them.

Perhaps I'm trying to put more colour into M31 than is really there but I felt it still looked natural (?)


It sounds and looks like your optical train is suffering from chromatic aberration a little (this would result in distinct deep blue/purple and deep red/orange rings around stars).

There are 3 things you can do, depending on what is causing the rings and your preferences.
  • You can try the Bright Saturation parameter in the Color module
  • You can post-process in the Color module with Tracking off, using masks
  • You can use the Filter module's Fringe Killer mode to remove chromatic aberration rings.

Hope this helps!
Ivo Jager
StarTools creator and astronomy enthusiast
User avatar
admin
Site Admin
 
Posts: 1725
Joined: Thu Dec 02, 2010 10:51 pm
Location: Melbourne


Return to Image Processing Troubleshooting

Who is online

Users browsing this forum: No registered users and 1 guest