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Re: [ATM] Stepper Stuff

Thanks :-)

20 rpm sounds like a do-able solution with these
motors.  I might reduce further if I reduce the skew
rate at full speed.  I don't mind a few extra seconds
between movement for image steadiness.

Kevin

--- Nils Olof Carlin <nilsolof.carlin@telia.com>
wrote:

> 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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