GTOCP2 Control Box

Astro-Physics 400GTO, 600EGTO, 900GTO and 1200GTO mounts shipped from June 1999 to October 2003 featured high-quality DC servo motor drive electronics including the GTOCP2 Control Box. The following information pertains to that drive system.

These sophisticated, versatile mounts can be operated with the GTO handheld computer keypad controller alone or in conjunction with various popular software packages on your PC.

New and experienced observers will appreciate the many advantages of the GTO computer system. It allows you to locate objects easily in light-polluted areas where star hopping is very difficult. Even if you only recognize a few of the major stars in the night sky, you can explore the beauty of the universe. You can even polar align and find bright stars and planets in the daytime! The system also serves as a powerful educational tool, providing descriptive information regarding the object you are observing. CCD imagers and astrophotographers will set up their shots quickly to maximize the number of images that can be captured in a single night. You can even preprogram a series of objects that you plan to observe or photograph to be sure that you don't forget your favorites or new objects that you wish to explore.

The GTO Control System essentially eliminates the need to purchase additional accessories such as a polar alignment scope or mounted encoders and digital setting circles. Most of the functions of these accessories are included in the GTO Computer System.

GTO Control Box

The GTO control box contains all of the circuitry to drive the two servo motors and the logic required to circumnavigate the sky. This electronics box is mounted directly on the polar axis of the 1200 and 900 mounts and is a stand-alone unit for the 400 and 600E mount. We provide a pouch with a handle for the freestanding unit.

The main function of the servo controller is to drive the RA and DEC motors. The motors are DC servos with built-in shaft encoders. The rotation rate of the motors is controlled with a servo feedback loop. The servo looks at the return pulses from the shaft encoders and adjusts the current to the motor so that the rate is identical to the commanded rate (i.e. from .25x sidereal to 1200x sidereal). The servo is digitally controlled, and the shaft position is updated at a rate of 2000 times per second.

  • Machined aluminum housing provides robust protection for electronics.
  • Dovetail construction allows quick removal from 900 and 1200 mounts.
  • Removeable microprocessor chip allows upgrades in future.
  • 12V connector for locking power cable.
  • Connector for SBIG ST-4, ST-6, ST-7, ST-8 and ST-10 Star Tracker/Imaging Systems or any CCD with modular RJ-11 connector.
  • Two 9-pin RS-232 serial ports (DB9 female connectors) so that user can use DigitalSky Voice™ and a planetarium program (i.e. Software Bisque's TheSky software) simultaneously, if desired. The user must have two COM ports available on their personal computer to use the software together.
  • Focus connector - for 3.5mm phono plug (JMI or Meade electric focusing motors).
  • Reticle connector - for guiding eyepiece with an illuminated reticle that has a 3.5mm phono plug or the cable for our own Polar Alignment Scope.
  • 6 volt output accepts 3.5mm phono plugs to power Pentax 6x7 camera directly from the mount.
  • Northern and Southern Hemisphere switch.
  • GTO Keypad Controller locking connector.

Dimensions of servo box 4.9"x4.9"x1.8" (12.5x12.5x3.4cm
Weight 1.5 lbs. (0.7 kg)
Suggested power sources Portable 12V battery pack, auto or marine battery, 110 to 12V DC Power Supply (5 amp minimum, regulated and well-filtered to prevent spikes)
Standards Meets FCC requirements for home and office use.

Copyright © 1999-2019, Astro-Physics, Inc. - All Rights Reserved
This page was last modified: March 10, 2019

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