Signal amplification when summing low SNR images
Are the images properly aligned? Then you can usually add them all up and (for normalization) divide each pixel value by the amount of images that were added together. For $N$ images this will give you an SNR gain of

$$SNR_{+} = 10\cdot \log_{10}(N) \text{dB.}$$

This is under the assumption that the "signal" part of the images is always the same and that the noise in each image has the same power and is perfectly independent from the noise in other images. Hence, it is probably an upper bound on what you are actually going to achieve.