Is it my subs??

[Bizibilder]

I wonder if you could look at the attached images and comment please - I am wondering why my subs (which are light polluted) come out without that colour cast when stacked in DSS - they seem to have reverted to "orange" free!

Is there an explanation for this?

Could this, in turn, be an explanation why I seem to get "blue" images with very little red in them?

I have appended a thumbnail of my final stack form DSS - no processing at all, subs, and flats just to show the general colours.

[blinky]

DSS has an option that is probably on by default - something like reset all white balances - works wonders at reducing light pollution as you have shown!

[Bizibilder]

But it seems to kill ALL the reds!!

[blinky]

Yeah, either in photoshop or in DSS increase the colour saturation by 15-20% and you should be fine. Try switching it off and restack, then see if you can get rid of the light pollution in Photoshop. I would be very interested to see the results.

[Bizibilder]

I'm restacking with "RGB background calibration" - which DSS suggests is for "images difficult to post process". It makes a specific suggestion for unmodded cameras but you can't change it to that suggestion!!

[dph1nm]

"RGB background calibration" in DSS tries to set the background sky in the stacked image to have a neutral grey colour. Hence the lack of orange. If you want to keep the orange (why!?) then I think "Per channel calibration" will do so.

NigelM

[dph1nm]

One other comment I will make (which relates to your other thread) is that if you have too much light pollution in a single sub you are in danger of saturating your red channel well before the blue or green. If that happens, when you correct for light pollution there is a tendency for stars to come out blue/green. If you have really bad light pollution this can also affect galaxies. I used to have terrible trouble with the colour of M31 (in 1min exposures) until I bought a light pollution filter. Now I can do 1min OK.

My suspicion is that your subs may be too long, but it is difficult to tell from your example jpgs, as they get scaled in the camera.

NigelM

NigelM

[Bizibilder]

With a bit of help from several here (Blinky and Nigel M) and elseware(!) I have set up DSS to: "Use camera white balance" and "use AHD". The results of a swift hour on M51 are attached - obviously too few subs (will get more tonight) but i think an improvement. I have a SW LP filter in the post as I type this so I am hopeful that I can refine future images with that.

[Glider]

Looking good.

[Bizibilder]

Thanks again, Glider - I've been getting quite fretful over my "blues"

[Shibby]

It's a trade off - colour balance that's easy to work with, or colour balance that doesn't wipe out all the reds (or whatever casts you have).

Sometimes I stack with Per Channel Calibration then, in PS, give the red channel a little stretch before aligning the channels. I don't know if this is ideal, but I find in some cases it helps me retain more of the red data.