Re: ATM Compliant Focuser

["andrew barrett" <barrett@jolt.mpx.com.au>]

Donald Clement wrote

>I have been constructing a moving mirror focuser for an 8" Mak-Cass. It

this reminded me of an article I read a few years back in a local astronomy
magazine. it was for a normal newtonian not a mak, but the author
feels that most newtonian focusers (rack and pinion, helical, crayford)
are not suited for newtonian use.
instead he suggests using a sliding unit. 

"motion is parallel to the optical axis, ie. along the tube. the secondary
mirror
is carried along with the focuser so that the focal surface moves relative
to
the 'fixed' eyepiece mounting. it is very low profile and can be very
strong
making it ideal for astrophotography. I am by no means the first to suggest
this design"

I had been thinking of this but more so of a moving primary for my new
scope
( still heavily in design stage) or perhaps combining moving primary and
crayford.

I would appreciate any comments.

andy