Re: [APML]: Byers drive and the MototrakIV

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

Joseph O'Neil wrote:
> 
>         Just out of curoisity, you mentioned that you were able to adapt your
> autoguider to your older drive corrector.  I have an older drive corrector myself, and
> was wondering how you did this (for the "electronically challenged" like myself).
> thanks
> joe
> 

This may not be too easy for someone with little electrical knowlege.

First and most important, you must thoroughly understand, wire by wire,
the relationship of your existing hand controller to the dual axis drive
corrector, because this hand controller is what you will replace. 
In fact, this analysis attempt will tell you whether you are capable of
doing the interfacing yourself or not.  Be aware that some hand
controllers put out a 2 bit pattern (combinations of grounds and hots,
such as Parks) for the four directions and not just isolated contact
closures (or openings).  As a rule of thumb, the fewer wires between the
existing hand controller and the dual axis drive corrector, the more
complex the interfacing will be, because there will be cross-connections
within the hand controller you must duplicate in the autoguider cable.

Next, you need to decide whether you want to have both the existing hand
controller and autoguider connected at the same time or just one of
them.  (Parallel or serial connection of the two units will depend on
whether contact closures or openings move the telescope.) The SBIG
manual suggested circuitry assumes both active, which adds to the
complexity of the wiring but allows you to have the autoguider box more
remote from the telescope.  You don't really need hand control to
roughly center a guide star prior to inserting the CCD head if your
off-axis guider has a pivoting pick-off mirror and rotates such as my
Taurus does; I chose to have the autoguider box replace the existing
hand controller completely in the interest of simpler wiring and it has
worked out well enough.  The final final guide star centering and the
orienting of the CCD head for proper +X, etc,(I prefer to have it this
way in order to better understand the direction of the error movements)
is done from the autoguider box buttons while watching the readouts in
any case.

Some notes on the SBIG ST-4 - Be sure and order an ST-4 with the
unterminated 12 wire relay connector cable;  a brand-specific cable will
just have to be discarded or heavily modified.  The SBIG manual has very
good data on the relay connector pinout but their suggested interface
circuits are not much help.

In summary, it is hard to imagine a drive corrector that the ST-4 would
not interface with, but it requires some careful thinking.  If you do
not do the work yourself, check out carefully anyone who volunteers to
do it for you.

C. J. Klingman
Austin, Texas
klingman@onr.com