Quote:
Originally Posted by gregbradley
Mean versus Median. Rick has said Mean gives best Signal to noise ratio so I checked. In some instances it gave a tiny bit more but often it was the same.When it was better it was negligible but it does not remove noise as well as median. Mean is another word for average. Median is the midpoint in a set of numbers like 3,5,7 the median is 5 and the average is also 5. But in some sets the median and mean will be a different number.
A set of data that has some high numbers that are noise may show up better with median than mean/average. Say 3, 5 ,100 the mean is 36 but the median is 5. So the noise does not skew the image as much and odd values get dropped out as 100 is a long way from 5 so it shows up as an outlier ( a value that is outside the usual value of a set and therefore most likely noise).
If you watch the subs when using mean you can see it get more solid but some noise artifacts, satellites etc may not disappear. Now use median and as long as you have enough subs to make a meaningful statistical sample those artifacts will vanish.
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some stacking software such as RegiStar have a median/mean stacking function. meaning it rejects outlier data then uses the mean algorithm to average out the background noise component. best of both worlds. not sure if CCDstack has this option.