Hi Greg,
Not hugely. Here's the response of the same chip in an Apogee body:
Kodak's data sheet is available
here (PDF).
I wouldn't read too much into that comparison image except to notice that there are differences and that on the scale imposed by my 165mm focal length they aren't big in terms of how many pixels long they are. The Blue data is basically the 16 bit TIF file output by PixInsight stretched so that there is minimal clipping and then converted to 8 bit for web display and those differences could easily be emphasised with judicious processing. My problem arises from the size of the stars in that image as my chosen methodology is to remove the stars from any nebulosity images, process as seems fit and then add stars back from separate and much shallower RGB exposures which, because I have removed any nebulosity from them, can also be
slightly deconvoluted without risk of ringing. I might be able to reduce the bright star sizes in those long blue subs by using shorter exposure times but then I'd need to stack a lot more subs to recover the nebulosity. I'm always up for suggestions provided they fit in with my star removal methodology but I am really wondering if there is much to gain given the image scale. I wouldn't be trying to capture the reflection nebula in the Pleiades with the 165mm lens so is there much point trying to do the same for the flame nebula with that lens?
Sorry, I've rambled on a bit with this reply and I've got a bit further to go. I justify (to myself) the huge boost in Hα luminosity relative to the surrounding RGB stars in my images so far because without it the stars would overwhelm the image for most subjects. Similarly, I justify a very non-linear stretch of the Hα data because the eye, not to mention the average computer monitor, couldn't easily accommodate the dynamic range. I've yet to get into narrowband imaging at wavelengths other than Hα but I know I'm not only going to have to employ similar tricks but also compromise still further by boosting the brightness of, say, OIII relative to Hα to prevent the Hα from totally overwhelming the OIII. And that's not even getting into what palette to use.
As I see it a similar problem exists when combining reflection nebulosity with narrowband Hα data. How to choose the relative brightness? If I reference the blue reflection nebulosity luminosity to the stars responsible for it then, because I choose dim stars relative to the Hα, you'd never see it. If I boost the reflection nebulosity luminosity so that it compares with the Hα then one ends up with what effectively is a false colour image. As you know, I play tricks with the Hα when I colourise as I allow more white through for the brightest bits but I'm not convinced about then adding blue to the mix for the reflection nebulosity. One either ends up with magenta or one arranges for the blue (or milky blue) to mask the red of the Hα to some degree. The former may be more honest but looks, to my jaundiced eye, rather odd while the latter isn't honest at all as there's little physical justification for it and I doubt it would even really work.
Forgive me. If your after dinner slurp of Christmas port hasn't sent you to sleep then this post will almost certainly do the trick! I've said nothing that you, as an experienced astrophotographer with some cracking imagery, won't have worked through years ago. I guess I've shared so you know where I'm coming from in my quest to combine disparate data in as honest a way as I can while still producing visually appealing results. I've not got many answers yet but I'll get there and hopefully I'll be happy with the results when I do...
Please keep the feedback coming as and when you feel so motivated.
Bob.
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