[Moon-net] Parabola Geometry Resources

[Pat Barthelow]

Folks:

I am anticipating obtaining geometric surface data for the Jamesburg Dish, 
most likely a table of radaii  from the vertex outward to the edge of the 
dish, in probably 1/4" increments.  For each increasing .25 inches outward 
from the vertex, I will have a vertical offset distance to the surface, with 
the center of the vertex having zero offset, and the edge of the dish having 
the maximum offset, equal to the depth of the dish.   The Jamesburg 
cassegrain design, main  dish surface is not a parabola, but a "special 
shape" for enhanced gain, designed in the Mid 60s.  I would be interested in 
any existing dish or geometry software from the web,  that can generate such 
a table for parabolas, given necessary inputs of Dish Diameter, Dish  Depth, 
and the Focal Length.   (I think those three items uniquely define a dish 
surface.  I want to see where, and how much, the shaped dish surface 
deviates from a simpler, normal parabolic shape.

Also, does anyone know how a big dish's subreflector is fabricated?  Ours is 
10 ft diameter, and about 3 ft thick.  It must be  a very major undertaking. 
    How does one fabricate  an aluminum surface to the desired mathematical 
shape with any precision?

Sincerely, Pat Barthelow     aa6eg at hotmail.com
http://www.jamesburgdish.org
Jamesburg Earth Station  Moon Bounce Team
http://www.cq-vhf.com