From: "pdk" 
To: "atm" 
Reply-To: "pdk" 


.
>
> >  2. I just read in a recent ATM message: "... and dont use soft rubber
> roller
> >  blade wheels or your scope will float like a boat"

The preceeding message was included as a warning for folks who see pictures
of an early prototype of an equatorial platform a friend and I made. We
doubted our ability to make a "perfect" sector, so we thought the
urethane would average the flaws down due to the spread of the contact
area. That it did, and more.  It was fine the first few nights I used it.
Then the breeze
came.  :-(

bottom line...   plain old bearings.

as far as radius of the cone on which your sectors are based I can report this.
if you use the following assumptions... A CG of approx 24 inches.
A 1/4 20 threaded rod.
A very stable dob.
A judiciously chosen stepper motor.* A basic stepper controller that half steps.

You will be hard pressed to see flaws in the design. Construction flaws MAY
be a different story, mine you cant not that it does not have them, I nor
the experienced viewers I have had observing with
it, saw them to be an issue.
I still personally would opt for a "slightly" longer rather than
shorter radius due to the
enhanced gear / step size.

PK

--- BBBS/NT v4.00 MP