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RE: Flats

Last time the subject of flat targets came up all kinds of
devices were proposed.  The problem is to use the "right"
color light and to get it evenly illuminated.
In theory the best target is made from a large sphere that is
white on the inside and illuminated by a pin hole.  The sphere
needs to be about several times the diameter of the lens.
I guess the light bounces around inside until it become even.
The telescope looks in from a hole cut in the sphere.  It is
easy to see why these are not used in professional observatories
but with the small size of the Mk IV optics a sphere would be
easy to make.  I made one once by covering a large toy beach
ball with newspaper strips soaked in starch.

=====
Chris Albertson 
  Home:   310-376-1029  chrisalbertson90278@yahoo.com
  Cell:   310-990-7550
  Office: 310-336-5189  Christopher.J.Albertson@aero.org

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