1200GTO German Equatorial Mount (1200GTO)

Includes Go-to Keypad Controller and DigitalSky Voice™ software

Modern CNC machining methods inspired our mount designer to carve out the excess material in both axes of the 1200 and 900 German Equatorials while retaining a heavily ribbed structure for internal strength and rigidity. A unique dovetail was machined into the mating surfaces of the R.A. and Dec axes. This feature allows quick and easy assembly in the field without any tools. These mounts are truly a marvel of engineering - maximum strength and rigidity with minimum weight.

Motions are smooth and positive in RA and Dec with the hand controller or when manually moving the telescope. Each shaft is supported by 5 bearing elements, two preloaded ball bearings and 3 sets of massive thrust bearings. The result is very low friction, which is constant with the load.

The 1200 equatorial is equally at home in a permanent observatory or as a portable mounting for remote star parties thanks to the ease with which the two axes come apart. This is the perfect mount for a large refractor, Newtonian, Cassegrain or astrograph.

Mechanical Features

Specifications of Equatorial Head

R.A. worm wheel

10.3" (26.2cm), 225 tooth aluminum

Declination worm wheel

7.2" (18.3cm), 225 tooth aluminum

Worm gears


R.A. shaft

3.35" (8.5cm) diameter

R.A. thrust bearings

9.5" (24.1cm) diameter

Dec. shaft

2.36" (6.0cm)diameter

Dec. thrust bearings

6.5" (16.5cm) diameter

Latitude range

20 to 68 degrees

Azimuth adjustment

Approximately 14 degrees

Right ascension

4-minute increments, pointer, engraved both


1 degree increments, engraved, pointer

Setting circles

Porter Slip Ring design, engraved, pointer


140 lb. (63.6kg) instrument, depending on length

Weight of equatorial head

91 lbs. (41.4kg), Dec axis is 30 lbs. (13.6kg) , RA axis is 47 lbs. (21.4kg), counterweight shaft is 14 lbs. (6.4kg)

Servo Motor Drive

The drive system uses a high-quality zero-cogging DC servo motor controlled by a microprocessor to an accuracy of 0.05 arc seconds per step. Tracking is very smooth, noticeably smoother than any stepper motor drive or inexpensive servo drive. The system can be accurately controlled over a speed range of 4800:1 which allows 0.25x sidereal for guiding to 1200x sidereal for 5 degree per second. The circuit draws only 0.4 amps when tracking the stars, 2 amps with both motors slewing and requires only 12 volts to operate. This servo drive will satisfy the requirements of the sophisticated, advanced astrophotographer, yet is easy for the casual, visual observer to use. Please refer to GTO Control Box and Keypad for Servo Drive for additional information.

DigitalSkyVoice™ Software

DigitalSky Voice is a terrific observing companion offering lots of observing ideas and information. If you plan to use an IBM-compatible personal computer to control your telescope, you will have lots of fun with this program. The software is included with the mount. Please refer to DigitalSky Voice Software for additional information.


The diagram shows several dimensions that are commonly requested. In addition, if the scope is horizontal and pointing west or south, the measurement from the top of the pier to the middle of the cradle plate is 11.25." Please note that these dimensions will vary somewhat depending on your latitude. We quote them for 42 degrees because that is the latitude of Astro-Physics and all of our equipment is set up that way. It is also a good average value.

Price and availability

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Available Options

You may wish to consider these accessories:
Santa Barbara Instrument Group ST-4, ST-6, ST-7 and ST-8 CCD Star Tracker/Imaging Systems
Jim Kendrick Studio Kendrick Power Supply and 17 Amp-hr. 12 Volt Rechargeable Battery Pack
Portable Pier - 10" diameter, heights 24",32",42",48",54",62
Mounting Plates- FP1800, DOVELM, 1200RP,1200RP15
Stainless Steel Counterweights 10, 18 lbs
Special 26.9" Counterweight Shaft (M12661)
Pier Accessory Trays and Support Bar
Jim's Mobile Inc. Digital Setting Circles
Cable for SBIG ST-4, ST-6, ST-7, ST-8
Encoders for Digital Setting Circles
Mounting Rings

Refractors   German Equatorial Mounts   Accessories
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Kendrick Dew Removers & Power Packs

Copyright © 1999, Astro-Physics, Inc. - All Rights Reserved
This page was last modified: October 19, 1999

Astro-Physics, Inc.
11250 Forest Hills Road, Rockford, IL  61115, U.S.A.
Phone: 815-282-1513   Fax: 815-282-9847