Re: ATM Re: Worm Fabrication

[andydtg@phoenix.net]

Bob Pfaff wrote:

>I not sure I follow the scenario

I'll try to re-state it - the idea is to compare an unknown drive
against a known good drive, sort of like measuring a lens against a 
test plate. You eliminate the overall curve & see the differences
as a fringe pattern.

As the drives run in opposite directions, the error-free part of the
rates cancels, what's left is the amount the drive being tested
leads or lags the reference drive at any point in time. This
shows up as a change in the direction of the normal to a flat mirror
mounted on the tested drive (the normal is at 90 deg to the drive
axis). The autocollimating telescope/camera sees this error as 
a change in the position of the star.

>but here is a tip on
>how I made accurate lead screw drive to pull a thin steel belt
>to drive a telescope. <snip>

Really ingenious! I probably won't have to go to those extremes,
I have a 6" long 5/16-40 micrometer leadscrew & nut, this at a
radius of 5' will have a scale factor of about .00029"/arc sec 
& should be good enough, at least for what I'm trying to do.


Andy Saulietis / DTG Alt-Az-Fp Drive Systems
12617 Harriet Ln
Santa Fe, TX 77510 USA
409-925-8854 Voice/Fax