[Laser] Re: Lunar Eclipse #3

[James Whitfield]

From: "Tim Toast" :

"This is all assuming the moons limb reflects just as well
as the center does, which it seems to do. I did read the
limb has a higher albedo at optical wavelengths than at
radio and that there is a pronounced limb darkening at
radio wavelengths."

I suggest an experiment to measure the optical reflectivity across the
observable face of the moon.  Take a picture of the full moon, then compare
the "brightness" of the pixels.  You might need to use color filters if you
want to get data on different frequencies of light rather than a composite.
It may be necessary to distinguish between plains and mountains, which may
provide different results.

I had started to suggest looking at the full moon in a telescope, but there
may be a psycho-optical effect at the edge which is surrounded by dark sky.
My recollection, from limited, casual observing, and never with proper
filters for the brightness of the moon, is that the center of the full moon
is brighter than its edges.

I am not sure what value it might have, but if you have a laser
communication system that can in some way measure signal strength, you could
point the "dot" on a piece of cardboard or construction paper, then aim the
receiver at the same spot.  By changing the angle of the cardboard relative
to the beam, you could see if the reflectivity versus angle will match what
can be observed on the moon. Trying other material, you might find an
optical model for the texture.


James
 n5gui