[Laser] Astronomy frame stacking software

[F1AVYopto at aol.com]

James
> Suppose that you have a message  that lasts about three minutes if sent as a
> 1 baud BPSK signal with a  carrier tone of 1 Hz.  If the CCD is sampling 10
> frames per second,  you get about 1800 frames.  With the modified image
> stacking  software, you look for clusters of pixels that fit the pattern of 
5
> or  10 frames of increased brightness followed by 5 or 10 frames without.
>  Then you rescan the images to find the synchronization, which is basicly
>  choosing the grouping that minimizes the sets of 10 frames that show  more
> than 6 bright.  Then group the images ten at a time, if the  first 5 are
> brighter than the rest, it is a one, if the last five are  brighter it is a
> zero.
This principle could be very sensitive at very  low rate.
It is already used to display the optical pulsars with a  stroboscopic effect.
The CCD accumulates the OFF picture separately during  the ON picture with a 
rotating shutter in front the lens.
The light variation  increases with the time.
If the speed of the shutter is well chosen, then a  beat occurs in the 
averaged sequential pictures.
With a very long integration  time a very small light variation could be 
detect.
Example can be seen at:  
http://www.tass-survey.org/richmond/crab.html
73 Yves