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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 or multiple batteries. 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 starting up the
GTO. Or, better yet, put the dew heaters on a separate battery.
The motors sound louder and more labored in cold weather.
As the temperature drops, we recommend that you reduce your slewing speed to 600x. The cold causes the lubricants to
get stiff in the gearboxes. This can make the high- speed gears resonate and sound screechy. Lowering the slew speed in
winter will eliminate this. You might also want to add a drop or two of light machine oil to the center posts of the individual
gears. Just remove the cover on the gearbox and add the oil drops. The noise is nothing to worry about
.
Refer the section of
this manual entitled: Slewing Your Mount in Below Freezing Temperatures.
If any problems occur, please don't hesitate to contact Astro-Physics for assistance.
ASTRO-PHYSICS INC
11250 Forest Hills Road
Rockford, IL 61115
Telephone: (815)-282-1513
Fax: (815)-282-9847
www.astro-physics.com
Recommended Reading from our Staff:
The Backyard Astronomer's Guide, Terence Dickinson and Alan Dyer, Camden House Publishing, 1991
The authors, both former editors of
Astronomy
magazine, offer practical insight into astronomical equipment, finding your
way around the sky, polar alignment, using setting circles, and astrophotography. This book provides excellent explanations
and is well organized and illustrated.
All About Telescopes, Sam Brown, Edmund Scientific Company, 1975. Excellent information regarding the
principles of mount construction and operation, using setting circles, eyepiece projection, etc. Illustrations and formulas
galore. Many of the instruments pictured are outdated, however the underlying principles are timeless.
Norton's 2000.0 Star Atlas and Reference Handbook, edited by Ian Ridpath, J. Wiley Publishers, 1989.
Star maps, information regarding polar alignment of German equatorials and observing techniques.
Summary of Contents for GTOCP3
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