ngc 3628

[alacant]

Hi everyone

We've a fast reflector for the weekend which despite having been bounced around on the train from Madrid yesterday, needed only a quick tweak to satisfy our Cheshire.

Last week, we posted in the beginners' section about galaxy colour, but drew a blank. I wonder if there are any guidelines as to their colour? In this example we let Siril's star database -it makes all stars almost colourless- do the colour and let the galaxies look after themselves. It's quite confusing looking at the colour variations during a google image search so for now, we're giving up!

All comments, colour or otherwise most gratefully received. Cheers and thanks for looking.

 

eos700d

Edited March 1, 2020 by alacant
capture details

[wimvb]

I use photometric colour calibration in pixinsight. It seems to do the job ok. But the final colour depends very much on how you stretch the image. Mark Shelleys arcsinh stretch (available in pi and Photoshop) keeps colour ratios far better than other stretches. To keep colour in the stars, you have to be careful during data capture, and during stretching. Stretching will inevitably lead to bloating of stars, which also means white stars.

[alacant]

9 hours ago, wimvb said:

arcsinh stretch (available in pi and Photoshop)

And Siril...

9 hours ago, wimvb said:

which also means white stars

Yeah, I think I get it. It's just that I can have as much colour as I like -artistic- but that doesn't agree with what the database colour says it should be. Dilemma!

[wimvb]

Have you tried making two versions? One artistic, where you throw science out the window, and one as close as possible to being scientifically correct. Then evaluate both and figure out how you can get the best of both worlds. In my personal opinion, as soon as we start stretching an image in various ways, and start using masks, we've basically decided to throw much of science out. A good astro image is aesthetically pleasing but also has a story to tell. The image doesn't have to be strictly correct, but it shouldn't deviate too much from "the truth". That part of AP is always a personal balancing act.