Re: Help with AP GTO on Parallax 125

Tim Khan


Check if the setting on your hand controller is for
the proper mount. On the AP mounts you can set up the
hand controller for the 400, 600, 900, and 1200
mounts. Choose the correct one for your mount.

Remove your shims.

Alternate method for Othogonality:

Do a star drift alignment, get alignment very
accurate, center a star on the same hour as Polaris,
calibrate with that star, and slew to 90 degrees Dec
and same hour angle, check if setting circles agree
with computer. Doing this should prevent a change in
RA when slewing, just incase something is wrong with
the RA. Insure that you are pointing exactly 90
degrees in dec. If unsure of the Dec, pick a star and
manually slew using the mechanical setting circles to
90 degrees.

Rotate Mount with RA only. Look using medium to high
power through the scope. The stars in the field should
rotate perfectly around centered of the field, if not
your orthogonality is off, you can shim either ring to
bring the orthogonality in. Remember, you must be
polar aligned, and be point perfectly 90 degrees Dec.

Now slew to a star, like Regulus, recalibrate on the
star. Try slewing to other stars to see if it is
pointing properly.

I hope this helps.


--- Mike Mah <> wrote:
AP 155 EDFS, AP rings on 16" Parallax Dovetail on
Parallax 125 with

I have had this out several times now and have been
unable to get it
to point accurately - place and time setup are

On calibrating with Polaris, I have used Pollux, but
after several
iterations, whenever the mount slews back to Pollux,
it is always off
by a couple of degrees and I have to push the East
button to
re-center Pollux. When it slews to Polaris, Polaris
will be centered.
When I slew to another object, I can find it by
pressing the East
button for the same period of time.

I haven't checked for orthogonality using the method
in the manual -
I don't know which stars straddling the meridian to
use and I can't
stay up later to use Arcturus as per manual. On spec
and assuming a
one degree error in orthogonality, I shimmed up the
front rings by
one quarter inch tonight and it didn't seem to make
any difference.

Even when I recalibrate on Pollux and then slew to
Castor there is
still variable error of about half a degree.

Any ideas?

Mike Mah

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