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Setting strut length for my telescopes and kits.:
 
 


Setting the strut length when building one of my kits is pretty easy. Here's is a simple procedure:

A -- Set the focuser travel to one-half the distance (if the focuser draw-tube travels 2", set it at 1").
B -- Measure the distance from the center of the diagonal to the top of the draw-tube.
C -- Measure the distance from the underside of the front ring to the center of the focuser.
D -- Calculate the distance between the secondary and the front of the mirror (see below).
E -- Measure the distance from the front of the primary mirror to the front surface of the mirror board.
C+D+E -- Add these numbers for the strut length

 

 
Here's an example of a 10" F4.5 telescope with a focal length of 45":
  Description Measurement
A set the focuser at 1/2 the draw-tube travel  
B center of the secondary mirror to the top of the focuser............................ 10"
C underside of top ring to center of focuser........................................................ 2.5"
D the focal length of the primary "minus" B -- 45-10=35.................................. 35"
E surface of the primary mirror to the upper surface of mirror board...... 3
C+D+E strut length = 40.5"....................................................................................................... 40.5"

For more information about your requirements:
--Dennis Steele
--Tel: 650-315-6578 (anytime)
--Email: densteele@dobstuff.com




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