RGB processing help needed

[hobbit]

Hey all,
I decided to try my hand at some RGB imaging and took 10x300 sec each colour of IC4604.

I stacked each colour individually in maxim dl and then tried importing each colour into star tools using the RGB function.

After that I hit auto develop and based on the results I think I definitely missed a step somewhere.

Any suggestions?

[alpal]

I use Deep Sky Stacker , then FITS Liberator then Photoshop
with some help from Fitswork4 -
so I can't help you.

You may be doing things the hard way.

[irwjager]

Hi Hobbit,

Sounds like you're doing everything right! However, keep in mind that AutoDev is just the start of your processing and any stretching you perform merely acts as a visual aid for you to see what you're doing (in StarTools you redo your stretching as many times as you like).

AutoDev in particular will help you find issues in your data, since it creates a stretch that is optimised to show every little detail - warts and all.

Without seeing what you end up with after the initial AutoDev, chances are it will highlight stacking artifacts, dust donuts, color bias, light pollution, gradients, dead pixels, etc.

Deal with these issues one-by-one and after dealing with each, re-stretch. You will get closer and closer to a 'clean' data set upon which you can base your 'real' post-processing, including your 'real' global stretch (for which I exclusively use AutoDev these days).

If you can't figure things out, shoot over your data (Dropbox or similar) and I'll do you a personalised tutorial. In the meantime also have a look at the YouTube video where M33 is processed from LRGB data (https://www.youtube.com/watch?v=nk3zTZzd9kY) - it should deal with very similar issues.

[hobbit]

Hey Ivo.
I think color bias would be the right word for. The whole screen goes blue

[irwjager]

Yep, that's a typical thing to happen (in the M33 and M8 videos it's a strong yellow). Don't panic when you see that - it's just AutoDev trying to tell you 'this needs fixing!'. Just make sure your data is 'Wipe' ready (e.g. make sure it doesn't contain artifacts or 'darker-than-background things' that are not part of the real image).
Then go ahead and run the Wipe module.

After Wipe and running AutoDev again you should get something decent (turn on Temporary AutoDev in Wipe to see what the data would look like stretched), or AutoDev may show you the 'next' problem to fix. Don't worry too much about correct coloring of the detail at this stage - just worry about the background looking ok (nice and even and devoid of obvious colored patches). StarTools (uniquely) performs final color calibration last (before switching off Tracking and doing noise reduction).

The M33 video (and also M8 video) should explain what's going on and why things are done the way they are done.

[hobbit]

Thanks Ivo

[hobbit]

On the upside it's not a screen of blue anymore.
http://www.astrobin.com/91100/

[irwjager]

Well... you're getting there, but there are lots of things still in the image that are 'darker-than-background' and artificial. Crop these away - AutoDev should make them readily apparent (they are in the Astrobin image). You have stacking artifacts at the top (causing Wipe to back off and leave blue), bottom, left and right. Your flats didn't work very well as there are a good few dust donuts. You can mask these out though, for example with the Lasoo tool (so that Wipe doesn't sample them for background pixels). There are dust specks as well - bump up the drak anomaly filter which will filter out smaller dark anomalous data like the dust specks.

And of course, you're going to have to align the red, blue and green channels - preferably during stacking (by taking one of the channels as a calibration source). If you can't, then you can 'abuse' the StarTools' Lens module to shift red and blue into place to line up with the green channel - make sure to crop the alignment artifacts after that procedure.

Bottom line is; make sure you give Wipe (and Startools as a whole) data that is as 'real' as possible, without artificially introduced errors,artifacts or dark anomalies!

[hobbit]

I'm thinking a brick would come in handy about now

[irwjager]

Let's take it from the top.

Does this help? (from the Maxim website)
http://www.cyanogen.com/help/maximdl/Align.htm

Get that data in shape and your life will be so much easier! Here to help.

[hobbit]

Ahh.
I didn't realize you could do all colors at once.