Telescope Control Systems

Sidereal Technology Servo II

The MI-500, MI-750, and MI-1000 mounts are normally supplied with the Servo II computer control from Sidereal Technology. This is the standard computer control package we ship with each mount. This control has a rich set of features including the following:

The Servo II control supports German and equatorial fork mounts, as well as altazimuth mounts. It has an open architecture that gives access to nearly every motor and control parameter. Using Pittman 9000 or 14000 series motors, the Servo II provides a motor encoder resolution of 0.10 arcseconds per count.



The Servo II control features a PEC sensor on the RA worm shaft that records the phase of the worm rotation. A periodic error profile can be applied since the phase of the worm rotation is always known, even after powering down the control. The PEC does not depend on timing the rotation of the worm. Rather the worm phase is determined by the sensor on the worm shaft.

The Servo II also supports mount homing. The feature enables telecope control from a remote location. Homing disks are intalled on the RA and declination axes. A sensor on each axis records the home zero position.

When the mount and control are first turned on, a command is given to find the home position. The servo motors move each axis, searching for the zero position as measured by they home sensor. Once located, the position of the telescope in local altazimuth coordinates is known. From the local sidereal time and the longitude and latitude of the observatory, the position of the telescope in equatorial coordinates can be calculated. The observer knows where the telescope is pointed in the sky, whether in the observatory or on the other side of the world. The Servo II control is ASCOM capatible, so it can be used with many popular astronomy programs to control your telescope. Using your laptop, you can position the telescope, center an image and control the tracking rate, and then park the telescope at the end of the night.

The Servo II support high resolution encoders.Ring encoders are installed on each axis. An electronic read-head record axis motion independent of any errors in the motor gear head, the worm gear, and timing pulleys. These ring encoders provide .10 arc second resolution on each axis. They have typical error profiles of plus/minus 4 arc seconds over 360 degree (pointing error over the entire sky) and short term errors (tracking errors) of plus/minus .20 arc seconds. Even these small errors can be modelled and reduced.

The encoders (British Renishaw encoder rings) are integrated into the mount during construction. The components that support the encoder rings are made of thick stainless steel to provide a thermal barrier between the encoder ring and the large aluminum components in the mount.

This Servo II control requires a 12-28 volt power supply with a minimum output of 5 amps. A variable voltage supply is recommened.


AstroPhysics GTO3

As an option, we offer the AstroPhysics GTO3 computer control for our M-500 and MI-750 mounts. Using Swiss DC servo motors, this drive system provides smooth tracking with motor encoder resolution of 0.10 arcseconds per encoder count. The GTO3 has a speed range of 4800:1, which provides 0.25x sidereal rate for guiding and 1200x sidereal rate for slewing.

The keypad is a handheld computer with the features and functions to control a telescope. The GTO3 control can be used with a laptop or desktop computer in conjunction with planetarium software. You can position the telescope, center an image and control the tracking rate, set the reticule brightness, and then park the telescope at the end of the night. This GTO3 control requires a regulated 12-18 volt power supply with a minimum output of 4 amps. This control can be purchased as an option with the MI-500 and the MI-750 mounts.


Bisque Telescope Control System (TCS)

As an option, we offer the Bisque TCS particularly for those needing to operate their telescope remotely. This is a sophisticated control system that includes a complete software suite, including TheSky and its remote control scripting program. This is the same control system used with the Paramount ME, well known for its precision and portability. It includes periodic error correction, 56 bit internal precision, and many other advanced features.

The TCS is designed to be used with an external computer using TheSky software, which has excellent remote control capabilities. TheSky is a well known planetarium program with many telescope control features.

We have adapted the TCS servo motors to each of our mounts with special 12:1 reduction brackets using timing belts and spur gears. This control can be purchased as an option with the MI-500, MI-750, or MI-1000 mounts.