RGB subs: very short for stars plus longer for nebula?

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Frank Alvaro avatar
After about 18 months of using a OSC camera, I've just ventured into mono imaging.  I've seen that many people use brief subs to record RGB colour and longer and more numerous luminance subs for details.  I've done this for my first two LRGB images, using 30 second subs for R, G and B and 300 second subs for luminance, and they seemed to work out OK (see below). But I see that the stars still seem to have white, blown out cores, so I thought I should decrease the time for the RGB subs to something like 10 seconds...but then I wondered if this will be enough to capture colours in nebulosity. 

So my question is: would it make sense to take 10 second RGB subs just for star colours (not sure of the total duration - maybe 10 minutes each?)  and then longer and more RGB subs to get more nebula colour? The plan would be to extract the stars from the briefest processed RGB image, extract a starless image from the longer RGB image and process that, then combine those with the luminance. Would this necessarily make a better image, or would just using a large number of very short subs give me good star colour and sufficient nebulosity colour?

Frank



Corona Australis Nebula, NGC 6729




Eta Carina Nebula, NGC 3372
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andrea tasselli avatar
Your problem is more with the luminace data rather than with the RGB data. I'd suggest you process the RGB image properly (i.e., in line with the luminance one), extract the stars, create the LRGB , remove the stars and put the RGB star back into the LRGB image. BTW, you white point seems a triffle too low to me, if you want to show colors in the highlights.
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