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    Re: Lunar Distances with Alex's SNO-T
    From: Bill B
    Date: 2006 Nov 13, 00:12 -0500

    Regarding the "laser" beam
    
    Bill you wrote:
    "Is there any reason one could not dispense with the scope and use a
    zero-magnification sight tube to take the optics out of the system?"
    
    Frank replied:
    
    "Yes, you have to focus the beam. Your worry that the telescope focus is
    related to the index correction is wrong. Just to remind you, the whole
    point of doing a "table-top" test of index correction is to take the human
    eye out of the equation.
    
    By the way, from my perspective, lasers are common-place. You can buy small
    ones next to the candy at the check-out in any hardware store. The nice ones
    with levels and on-off switches are in the back of the store. But if you
    find lasers "exotic" or if they seem like a cheat (assuming you like to do
    things in antiquarian fashion), then you can use any focusable light source
    with a sharp image. For example, you could project a pattern of lines using
    an old slide projector. I'm not saying that I recommend this --a laser is
    the right tool for the job."
    
    Frank
    
    Agreed to some point, but I seem to be suffering from a generation gap on
    the common usage of terms like "font" and "laser" that have been corrupted
    beyond recognition.  Graphic artists/typographers with traditional roots
    will understand my "font" reference.
    
    Having played with real lasers over 3 decades ago, I just did not expect a
    "laser" beam to have a spread on nominally 1/2 minute.  Figured the $30 to
    $40 laser pointers for-sale at office-supply stores might be some dramatic
    advance in technology (and off-shore manufacturing), and the $3-10 units in
    hardware stores etc. some form of focused light.
    
    Point being, I seriously doubt the lasers you refer to meet the standards of
    both monochromatic and collimated light. Hence the need to focus these
    b_astard stepchildren of a real "laser" beam.
    
    Slowly understanding. 
    
    Bill
    
    
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