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Old 06-10-2017, 05:51 PM
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Lognic04 (Logan)
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Combining data with different levels of light pollution?

Hi all,
Have been thinking about combining data from different levels of light pollution recently, because it's hard to get enough exposures in one night at a dark site to remove noise. I'm thinking that the data with more light pollution will kill off the fainter bits of the image. Would this actually work well?
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Old 06-10-2017, 06:41 PM
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billdan (Bill)
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In those situations it may be better to stack each night separately and then stack each stack as a median stack, as each stack is already calibrated you won't need to use darks or flats again.

EDIT: That's what I do with data that has been meridian flipped, stack each separately and then flip one of the stacks and then stack the two stacks.

Last edited by billdan; 06-10-2017 at 06:52 PM.
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Old 06-10-2017, 07:10 PM
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Atmos (Colin)
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It depends on how much light pollution you’re dealing with and how dark your dark skies are

If I was to try it on faint bits from my dark site and light polluted home, 1 hour of dark sky would probably equal around 6-10 hours of light polluted skies. This is in LRGB and not narrowband btw.
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Old 06-10-2017, 07:43 PM
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I kind of doubt it will work. You will just degrade the good dark site data.

I think you would be better off imaging just the brighter objects so you can get enough data to put together an image.

Also keep a library of your data so next year when you image that object again you can add the year's before data to the recently collected data.

Also the need to collect enough data quickly is why the trend is for largish aperture fast scopes with quite sensitive cameras and not oversampling too much.

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Old 06-10-2017, 09:05 PM
Alexborek (Alexandre)
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You can try to do a photometric callibration and extract the background brightness (and gradient) for further corrections. Not easy but works!
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