ASTRO-PHYSICS German Equatorial 1200GTO, Руководство пользователя

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TROUBLESHOOTING
Additional troubleshooting questions are in the GTO Keypad manual. Some of the issues discussed in the keypad manual
relate to mount communication issues whether you use the keypad or control the mount with a planetarium program or
PulseGuide. Please refer to them.
The Declination (or R.A.) axis is fairly tight, even with the clutch knobs fully loosened.
This occurs when the clutch plugs have been damaged from over-tightened clutch knobs. Please refer to the appendix at
the end of this manual for detailed instructions on clutch plug removal and how to fabricate your own clutch plug tool.
The LED on the GTO Control Box changes from red to yellow and the motors stop or go out completely (for
mounts shipped after 02-25-00).
1. 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 to reset the keypad. Re-enter the last object
on your keypad 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. As long as you didn’t change the pointing position of the
scope, you are still calibrated.
If the scope was moved during re-balancing, simply enter a nearby bright star on the hand controller, press GOTO
and allow the mount to finish slewing. You can then move the scope manually or with the N-S-E-W buttons to center
the star in the eyepiece, and press the #9 RECAL button. This will recalibrate the mount.
Additional explanation : The GTO drive circuit includes logic for overload protection to prevent burning out the
expensive servomotors in case of severe overload on the two axes. The primary cause is an unbalanced load in
R.A. If the extra load opposes the motor rotation, the motor must work harder to track at the sidereal rate and the
current will rise to high levels. If the current exceeds the trip point for more than a minute, the logic will shut the
motor off and tracking stops. It typically takes about 4 lb. of unbalance to trip the overload, but a very heavy load of
scopes, accessories and counterweights on the mount can decrease this unbalance threshold.
2. The voltage of your battery has probably gone below 10.5 volts.
3. The current rating of your AC-DC power supply is too low.
Additional explanation : During slewing, the two motors draw up to 3 amps from a 12 volt source. This may increase
when the temperature approaches freezing or below. It is recommended that your supply be rated at 5 amps, 12
volts DC minimum (18 volts max.). If you also power other equipment (CCD cameras, dew heaters, etc.) from the
same source, you will need a supply capable of up to 10 amps. The more equipment you have, the more current
capability you will need. For portable applications, we recommend a heavy-duty marine battery designed for deep
discharge applications. The most common problems are due to inadequate power supply.
The keypad reset (or locked up) when I plugged my CCD camera, PC (or other equipment) into the same
battery as the GTO mount was using. The battery has a meter, which shows 12V.
The meter is reading an average and will not show dips. Gel cells have internal resistance, which will cause voltage drop
when the load changes. When you connect an additional CCD camera and PC the load will drop below 9 volts and the
keypad will reset or it may affect the GTO circuit itself and cause the keypad to lock up.
We recommend that you use a large marine battery that is not a gel cell and hook everything up to it before calibrating the
GTO. Or, better yet, put the other equipment on a separate battery.
What is the maximum voltage that I can use to power the servo drive?
The servo drive of the 900GTO and 1200GTO will withstand up to 24 volts without any sort of damage to the internal
electronics, according to our engineer. However, above about 17 volts, the motors may become a bit jittery because of the
higher gain with this much voltage. The system works very well with 15 - 16 volts. Please note that for most applications, 12
volts works just fine.
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 have
still small drift in RA which looks like the RA motor is a bit faster than earth rotation. This drift is
something like 1.5 arcsec during 1 minute or so and is accumulated over time, so it doesn't look like
periodic error.
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.
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