Re: [ATM] The Public Terrestrial Telescope: Further Reflections and anUpdate on the Project

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

Remember when you are doing the focuser that you don't need to
have inches of travel as the E{ isn't going to be changing.
Also, yo can limit the near field by not allowing for that much
focus.  Generally, there is no need to focus to something a
hundred feet away so yo can take that into consideration.
The Rak and pinion focuser will work fine in that regard as yoe
will only need to put an o-ring at the EP tube and the two (or
better yet the one) end f the knob shaft to gain waterproofing.
Another way is to do a twist type focusing with a cam insidewhich
will rapidly change the position of the EP.  You don't need to do
a real fine focusing like the helical focuser that we use as the
user doesn't need to have that fine a focus but rather the speed
rate that the variable fofocal length EPs have.  That ends up
with only one o-ring needed for waterproofing.
FWIW, Washing machine grease is a nice waterproofing grease for
the seal.
Bob May
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