Quote:
Originally Posted by jase
Give it a try Terry. The sum is simply the sum of corresponding pixel in all images (of the data set you are combining). Pixel values increase, so you are perhaps increasing the signal, but at the same time noise also increases as there is no data rejection being performed. Undoubtedly, noise increases at a lower rate than signal, so I will acknowledge that it may not necessarily be "proportionate" as I originally indicated.
|
I have done this many times but not for images but for photometry. I sometimes take 3 x 5 min exposures of dim stars through a blue filter. I measure the S/N for the individual stars compared to summing the images. The S/N is much better on the summed image allowing measurement of the magnitude of a much dimmer star. I could take a 15 min exposure and hopefully have an even better S/N. I don't do this as sometimes the star is bright enough to allow measurement on the individual frames and I can average the result to inprove the accuracy.