Re: [ATM] Stepper Stuff

[Nils Olof Carlin <nilsolof.carlin@telia.com>]

Kevin,


>>>
The steppers I have are from old disk drives.  I have
a couple from the old TEAC 1/2 height 5.25's that have
some decent torque and work in 3.6 degree steps. 
That's 100 steps per revolution...  ok, that part's
easy.

I'm going to run the motor on a 8" f/6 Newt and
another on a 13.25" f/20-something Cass-variation. 
Equatorial, maximum magnification and stability is
desired, probably both forks with conical
right-ascension axles.

What's a good reduction for these motors so that they
don't go too fast when doing one step at a time?>>>

I would suggest that you aim for 25-30 fullsteps or halfsteps per 
second (the apparent motion of an object near the celestial equator is 
15 arcsec per second of time - 30 steps/sec is 1/2 arcsec per step) - 
there will be some inertia to smooth out the motion but there may be 
resonances in the telescope - perhaps in the secondary and spider, that 
can amplify vibrations.

This means 1 turn per 3-4 sec or so - 15-20 turns per minute or 900-
1200 per hour or 21600-28800 turns per 24 hr for fullstep (half that 
for halfstep), if I didn't miscalculate - this gives the total gear 
reduction to aim for. At least, don't go much below.

Nils Olof
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