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TROUBLESHOOTING, TIPS AND SUPPORT
Troubleshooting and Tips
Additional troubleshooting questions are in the individual mount manuals and in the Keypad manual. Some of the issues
discussed in the Keypad manual also relate to mount communication issues whether you use the Keypad or control the
mount with a planetarium program. Please refer to them. We will add to this section as we become more aware of issues
that users encounter.
Can I use the GTOCP5 control box with my other Astro-Physics mounts?
No. The GTOCP5 control box is designed to only work with the Mach2GTO micro-step motors. The other mounts use
servo motors that require a different electronics design. Additionally, the GTOCP5 control boxes are matched to the
individual Mach2GTO that they ship with. You'll note that they have the same serial number. You cannot use a GTOCP5
control box from one Mach2GTO with any other Mach2GTO mount.
The LED on the GTO control box changes from red to yellow.
1. The voltage of your battery has probably gone below 10.5 to 11 volts or the current rating of your AC-DC power supply
is too low.
NOTE: The most common problems are due to inadequate power supply!
Additional explanation:
We provide a 24-volt, 10 amps continuous, universal 85-240V power supply. Please use it only for your mount for best
performance. All other equipment (CCD cameras, dew heaters, etc.) should be powered from another power source.
2. You may have a poor connection at the supply pins or excessive distance between the power supply and mount servo.
What's important is NOT the voltage at the supply pins, but the voltage at the CP4 or CP5 control box. If there is a
poor connection at the power supply pins, you can easily have a couple of volts drop in the line going to the control box
and still read 13.7 at the power supply pins. We recommend that you keep your power supply close to your mount to
avoid a large voltage drop from a power supply that is placed too far away using a long cable. Do not add an extension
cable to the power cable that was supplied with your mount.
3. The motors are overloaded, probably due to an unbalanced load on your mount.
Rebalance your telescope, and then press one of the N-S-E-W buttons on your Keypad or computer program to reset.
Re-enter the last object and the scope will slew to the correct position. Even though your motors had stopped, the logic
in the control box retained the scope position in memory.
Additional explanation:
The GTOCP5 drive circuit includes logic for detecting a stalled motor on the two axes. The
primary cause is a severe unbalanced load in RA. If the extra load opposes the motor rotation, the motor must work
harder to track at the sidereal rate. If the motor stalls because of excessive load, the logic will shut the motor off and
tracking stops. Micro-stepper servo motors can not be damaged with overload. They simply begin falling behind their
commanded tracking speed, which is then detected by the logic. The amount of current drawn by the motor remains
the same for any load from zero to maximum overload before the stall point. Therefore, a stalled micro-stepper servo
motor will not heat up when overloaded or stalled.
For polar alignment, I am using declination drift technique with stars on east & south. Now, I do not see
any drifts in declination on both sites (E & S), so the mount “should” be properly aligned. However, I still
have small drift in RA which looks like the RA motor is a bit faster than earth rotation. This drift is some-
thing like 1.5 arcseconds during 1 minute or so and accumulates over time.
The sidereal tracking rate is exact in the mount (it is crystal controlled and checked here for accuracy). However, the stars
do not move at exactly the sidereal rate everywhere in the sky. The only place they move at that rate is straight overhead.
As soon as you depart from that point in the sky, the stars will be moving more slowly, especially as you approach the
horizons. Thus, it looks like the mount is moving slightly faster than the sidereal rate. Just because you have done a
classic drift alignment, it does not mean that the stars will now be moving at the sidereal rate everywhere in the sky.
Depending on sky location, there will also be star movement along the Dec axis.
In order to increase the area of sky from the zenith that will give you fairly good tracking, you will need to offset the polar
axis by a small amount. The amount will depend on what your latitude is. The other approach is to vary the tracking rate
for different parts of the sky.
