Processing advice: mixed 30s and 60s RGB subframes

[MicroAstro]

I started a project on IC405 the Flaming Star Nebula collecting 60s RGB subframes the first couple of nights, then I inadvertently switched on subsequent nights to 30s subframes. I used a QHY163M CMOS camera/60mm doublet.

It's rather complex what I ended up with:
R 30s x199
   60s x120
G 30s x56
   60s x176
B 30s x108
   60s x176

The total imaging time is similar: R (3.7h); G (3.4h); B (4h) but the balance of 30s and 60s subs for ea color is quite different.

How would you recommend processing these? Calibrate and stack all separately? Calibrate and stack ea color together (can I stack the 30s and 60s subs together for ea color)?

I also have nearly 10h of Ha taken with a different camera (Atik 383L)/telescope (90mm triplet) (smaller FOV but the image scales are similar: 2.2 arcsec/pixel for the Ha data; 3 arcsec/pixel for the color data). I'm thinking of using the Ha for luminance data (lots of resolution and texture) and blending it with the color data from the QHY163M.

Advice on how to approach this would be appreciated.
...Keith

[RickS]

Calibrate and register the RGB data with the Ha as the registration reference.  Then stack the 30s and 60s subs together for each colour.  They will be SNR weighted and you should get a good integration even with the mix of durations.  If that doesn't work then try something else 

[rdryfoos]

I have had no problem using subs of different durations.  Except it may not allow the use of  Mure Denoise if you use that.  If you don't scale your darks you'll have to calibrate separately--but if you have dark that are longer than all the subs BPP should be able to handle it.  One other thing--it may effect your star profile.  Longer subs have larger stars and I have had some stars look a bit odd--with more of a core/outer portion separation than normal.  But that was with subs that varied by 10 minutes or so, so you should be OK.

Rodd

[MicroAstro]

Great. That's what I was hoping to hear, that I could stack the 30s and 60s subs for ea color together. I'll get to work on calibrating then try that, registering to my best Ha sub.

...Keith