[ATM] Draw Tube Length

["Doug Williams" <salguod@minbaritm.com>]

Hi all,

 

I am getting a new Moonlight Crayford focuser for my 10-inch dob.  Since I
decided on the compression ring option, I have a choice of draw tube lengths
all at the same price.  The standard 3.3 inch draw tube has 2-inches of
travel.  But the optional 2.8 inch draw tube has 1.5 inches of travel, which
is enough to easily cover all my eyepieces at the height that I will mount
the focuser.  (I measured the height that my eyepieces come to focus).

 

I understand that the draw tube extending into the OTA a little bit is not a
big deal, but is there any reason why I shouldn't opt for the short draw
tube to reduce the distance that the draw tube intrudes?  I should also save
some weight with the short draw tube (though not much).  As long as all the
eyepieces can focus, is there any optical advantage/disadvantage associated
with draw tube length?

 

Doug

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