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Old 06-06-2011, 06:45 AM
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supernova1965 (Warren)
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Hypothetical Question

Can anyone tell me what the difference would be of taking 50 exposures of a star group and stacking them and making 50 copies of an exposure and stacking them. It is probably a stupid question but I tend to learn from asking them.
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Old 06-06-2011, 07:21 AM
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kinetic (Steve)
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Warren,

I think the key is signal to noise ratio.
If you stacked the same frames the noise duplicates (and is reinforced)
along with the data.

In a set of different subs, the noise tends to be random and is therefore
rejected as noise in a stack while the data is reinforced as true data.

The more frames you stack in theory, the more the noise 'drops away'
down to a mathematical noise floor.
You reach a point though, eventually where you gain nothing more by
adding frames....
Someone better versed in the maths can help out here.

Hope this helps,

Steve
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Old 06-06-2011, 07:23 AM
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bojan
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Steve is spot on.

Stacking process should be called "averaging" because this is what it is in a nutshell.
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Old 06-06-2011, 07:24 AM
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supernova1965 (Warren)
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I think you have explained that wonderfully I now know why several exposures is the best.

Thanks
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