Re: [ATM] Minimum Inner Tube Diameter

["Bob May" <bobmay@nethere.com>]

Actually the 2" theory is to allow for the end of the tube to
notbignete the image at the edge of the field.  The 2" EP has a
diameter of the FOV at focus of 1.7" or so which is pretty close
to the edge of the tube at the input end - the FOV of the largest
EP is what needs to be added to the diameter of the input end of
the scope to insure that the field isn't vignetted there.
IN addition, concrete form tubes are sold in even increment
inches and the s"standard" sizes of mirrors are also even
increments o f inches which works out well.
Bob May
bobmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net
Replace the obvious words with the proper character.

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