[magick-users] night shot merging multiple exposures

[Carl Karsten]

Klaas Decanniere wrote:
 >
 > Hello,
 >
 >
 > I am trying to make night shots with a ccd camera.
 > The maximum exposure time that can be set on the camera is 750 ms, which
 > is of course too short.
 >
 > Assuming the noise is random and the object I want to see does not move,
 > I should be able to improve signal-to-noise by taking the same shot
 > several times and  adding all the  images together

Using what I learned about CD error correction from http://www.xiph.org/paranoia/

I can see 3 approaches.  both involve using 3 or more shots.  the more the 
better.  for each pix:

1. look for the most occurring value.  use that value, discard the rest.  2, 5, 
5, 5, - use 5.

2. Given that there may be slight deviations even when there isn't noise,  sort 
the values, use the middle value.  10, 200, 201, 202, 205 - use 201.

3. looking at #2, if you can figure out that 10 is too far off and must be 
noise, then take the average of the remaining 202

Hmm, I bet this is a previously solved problem.

Carl K