Re: [APML]: Byers drive and the MototrakIV

["C. J. Klingman" <klingman@onr.com>]

This thread about the Byers Drive and JMI is not making any sense to me.

First of all, you surely must know the type of motors you have on the RA
and Dec axis.  If you have AC synchronous on both axis as I do, they
will be Hurst and clearly marked for 120vac use.  You will have good
photo guide capability but no slew capability;  have to bump the scope
from place to place by hand.  (AC synchronous motors cannot be driven
more than ~ +/- 30% of 60 hertz and that is pushing it.)  Of course, the
big accurate setting circles will make this much easier.

If you have stepper motors, you must have stepper motor drive circuitry
appropriate to the motors, and probably will not be integral to the
drive.  Overall, stepper motors would be best in order to have
controllable slew, but it will be expensive and difficult to find such a
dual axis controller if you didn't get one (or any documentation) with
the drive/mount.

I can't imagine a Byers mount with a DC RA motor although it may have a
DC dec motor.  

In any case, a JMI dual axis controller may or may not suit this drive. 
Standard JMI controller output is 120vac for a RA synchrounous motor,
+/- 12vdc for a reversible DC Dec motor.  I don't think you can get one
with the output for a reversible 120vac synchronous motor as used on the
Dec axis in my Byers mount.

I use an early 1980's vintage Kencor dual axis controller, which, by the
way, interfaced very well to an ST-4.  

C. J. Klingman
Austin, Texas