Anyway, Mooey, there is no such thing as a correct colour balance. A convenient reference for colour balance is White Balance which means the definition that sunlight looks white to us. So I think typically astrophotographers will white balance their images then tweak a little more for personal preferences.
Also, during imaging the altitude of the object changes, so atmospheric correction seems out of the point, unless the exposure is short or u only take pics when the object is at that altitude.
Is there a need for LRGB?
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just a thought here. am aware of the atmospheric correction values and have given this during the previous NUS-NTU AstroChallenge (last year). But in practice, I have not seen enough (perhaps not enough clear sky opportunity) to know if the correction is signficant enough to skew the colour balance. Being in an environment where severe light pollution exists, i think ultimately, we are still more concerned with coping with colour balance skew issues attributed to the light pollution effect on long exposures colour subs taken here in Singapore. Perhaps in really dark skies like in Arizona, or Chile, one would pay more emphasis on atmospheric correction values as advised in STARIZONA. The example on The Sculptor is evident enough. However, there is a fine line drawn between textbook and theoretical concepts and the practical field experience which we face an amalgam of possibilities and characteristics. Check out the wonderful mega mosaics of Rob Gendler taken in New Mexico. Now check out if he has wonderful mega mosaics taken from his polluted home town. No? None? Why? Possibly the additional challenge for poor folks like us here in Singapore yearning to master colour deep-space mosaiking would have to tackle light pollution normalisation issues first. It is not just a simple GradXterminator-ed mosaic component and then piece up everything together. Each normalised component will still need to be adjusted with the rest. And this is where the challenge lies. I'd realised that it is so easy to process images taken purely under dark skies. Very often, there is not even a need to do flat frame calibration, or correct gradient issues. But once it is taken in Spore, my hair starts falling when processing these local images. But if we take this in positive light, and learning processing metropolitan-based ccd images, and master it, we are already there at the top with the rest.
I think the big problem with the removal of gradient of each mosaic frame is because when the nebula fills up most of the frame, then it is hard to judge whether the gradient is due to the nebula or due to the light pollution. If the gradient is removed wrongly, the mosaic adjustments between the individual frames will be very tough to do.
Thats why H-alpha mosaics are easier to make.
LRGB also works for DSLRs and One-shot colour cameras. You can improve details dramtically that way. But due to the lack of control of the exposure of each colour channel seperately, The colour balance will be harder to adjust.
Thats why H-alpha mosaics are easier to make.
LRGB also works for DSLRs and One-shot colour cameras. You can improve details dramtically that way. But due to the lack of control of the exposure of each colour channel seperately, The colour balance will be harder to adjust.
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http://www.flickr.com/photos/14113965@N03/
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