Quote:
Originally Posted by bojan
Absolutely incorrect, I am afraid.
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Hi Bojan,
Read the deep sky stacker page I have attached in my previous post. I am afraid you are not correct.
From the article:
...Of course when you subtract one dark frame to one light frame you will remove the hot pixels which may give the false impression that the dark subtraction did its job.
However, at the same time the subtraction doubled the noise of the calibrated light frame and ruined it thoroughly...
And ICNR would be exactly one dark subtracted from the light unless some other filtering is applied (which I am not aware of).
Remember, while the noise is random, it still follows the standard error analysis and it is added when two signals are added or subtracted. If you have 16+-4 and 9+-3 the result from the subtraction is 7+-7 (and not 7+-1 as many people think).