[Laser] 21 mile daytime laser contact durin ARRL 10GHz & Up contest

[F1AVYopto at aol.com]

Kerry
A star is a punctual source but it is  also a not coherent and not 
monochromatic source.
With a laser the  scintillation is a very complex problem.
It is not only an erratic  convergence modulation with angular micro 
displacements associated with beam  global intensity fluctuations.
Constructive and deconstructive phase  combinations give beats that occur 
into the photo detector sensitive layer  because micro light speed modulation due 
to air density fluctuations.
This  beating effect gives a very deep granulation noise.
I suppose your multilayer  dielectric filter is fitted in a conical beam just 
in front of your photo  detector.
This mounting gives selective rings from the edge to the centre  with a 
strong bandwidth enhancement.
With the monochromatic laser light it is  possible the filter give a 
diffusing ring that reduces the scintillation by a  certain averaging on the 
convergent area.
May be the spot motions are  reduced?
May be the laser light coherence is partially lost after the filter  because 
its obliquity?
Normally a filter has no effect on the scintillation  by I had also noticed 
this effect and I cannot explain why?
73 Yves  F1AVY