--- In email@example.com
, "microboter" <jdavis211@...> wrote:
> Almost finished with my crayford style focuser. Its a low profile
> for 1.25" eyepiece. The height of the focuser base is 1" and I am
> curious about how long of a draw tube I should cut for it. The draw
> tube will have an OD of 1.5". This will be installed on a 10" f4.5.
> I was thinking 2 to 2.5" or so, think this will work?
The profile of a focuser with a fixed tube length, i.e. Crayford, is
not that of the focuser base, but that of the tube length. If your
focuser base has a height of 1" and you want 2.5" of travel, then the
tube must be at least 3.5" long. The profile is then 3.5" even though
the base may have a "low profile" of 1". Low profile and long travel
are mutually exclusive with a Crayford type focuser with fixed tube
Running Springs, California