[RCC] M101 Redux

Kevin Knight:
Thanks all for the input.  I started fresh from the stacked master and incorporated as much as I could with the knowledge I have.  I tried to keep it simple this time. 

Also did the following:

Did crop the image in a wider format to account for my small focal length. 
Did use SPCC after reading up on it and how to use it. 

Did Not mess with the saturation levels at all, only RGB/K in curves
Did Not use StarXT (that's a technique for future me)

I understand my scope is not really suited for Galaxy hunting but from my backyard that is all that is really being offered up in the ASI APP as visable.  When we first got the scope a bit over a month ago, we could see Orion's Nebula for about an hour or so, and it looked wonderful, so I am excited for the season to change  

I am also thinking of selling the Redcat, and purchasing an ASKAR V (I have one on preorder ATM). That will give me up to 600MM FL with the tradeoff of more exposure time needed which I'm fine with living in AZ I have plenty of clear nights. 

I added a new revision that I think looks much better. 



I have a few questions to ask if possible: 

Q. Are the reds in purples in everyones image just a mater of more exposure time? or is there a technique to that as well? 

Q. I have been saving all of my raw files since installing a NAS last week.  I have been saving each target in its own folder with Darks, Bias, and Flats which I shoot at the start of each night.  How should I handle multi night images in PI? do I just combine the 2 masters files, or do I put all the subs and calibration files in the same folder and run as normal? 

Thanks again for all the help.

I suppose I maybe should have clarified, since you're asking about the reds.   My image was shot in mono with Ha addition.   I was merely trying to show you the detail you can achieve at that focal length.    A lack of Red, or Ha data is a downside that you will always have with a color camera.  The Bayer matrix only allows you to grab one red pixel out of every 4, 2 pixels of green, and 1 for blue.  This is why (most) color cams are debayered as RGGB.  Mono efficiency will far surpass color any day.   This doesn't mean you can't still get the reds, but it's going to require a substantial amount of integration time and dithering to achieve it.  Also, that RGGB matrix is why (you've probably noticed) your images will appear very green until they are color calibrated.

I have two versions of M101 in my gallery, one with the 70mm and narrowband, the other is taken with a color cam and a longer focal length.  Feel free to check them out and you'll see a major difference.  

As for color manipulation, after you've color calibrated your data and stretched it, try not changing the RGB curves individually.  This messes with the color balance.   Instead try simply boosting the C (color) curve.    From there you can use SCNR mildly to tone down on the green overpowering the image.   This will again balance it out.   By that point you should see an image roughly resembling what most of us produce.   It will always lack red and blue, so this is why integration time is important.  From there you can use subtle curve changes to enhance your red and blue but chances are it will become noisy rather quickly.     

Lastly, apply a super STF stretch, then use histogram with live preview to adjust your black points so the background is neutral after any color curves.  

​​​​​This is pretty much the cliff notes version of how I handle OSC (color) data.   There is much more, like denoise, decon, etc but it's too much to explain right now.