Frédéric Géa

The 22" I used not long ago was on an equatorial platform made by John Lightholder. It was a good solution for this telescope. When I begin to think about the 32", it was impossible to go back and don't have a motorisation solution.

First choice, go for an equatorial platform. Problem, the eyepiece high is already about 9 ft ? The equatorial platform add about 4 to 6" and also add and angle of +/- 7 degrees. Second solution, look for a good altaz motorisation. Unfortunately I'm really bad with electronic stuff, impossible to have an homemade solution. Second problem, I don't want to have a notebook solution because I sometime observe in cold, humid weather. So I look for an easy to install and reliable solution. Starmaster Teslescope have the skytracker  but it is sold with a complete scope, so I forget it.

As the project takes shape, the solution was found ! Gary Myers started to produce is own tracking system, the "ServoCat". This solution exists in different packages (with computer, without computer, DIY ) hard not to find what you look for ! I choose the ServoCat Sky with servo motor, gearboxes. The digital circles required for the system was first the Skycomander and not long after, the new ArgoNavis. This solution doesn't required any computer once on the field of observation.

Servocat Handpad

The kit

In the kit I choose, we have :

-    The ServoCat electronic box

-    A handpad

-    Two servo motors

-    Two gearboxes

-    All necessaries cables

-    CD-rom for the configuration

-    Details instructions

Of course, you got to have the digital settings circles.


Argo Navis


Gear Box





Ball bearing for altitude movement



How it works ? The ServoCat asks parameter to DSC and give informations to servomotor. A very interesting feature : the Cat is not afraid to slip, you can engage/disengage the drive, have small slipping in the drive system, the Cat doesn't loose his position, it corrects it thanks to DSC position. The accuracy of the GOTO and tracking only depends on the accuracy  of the parameters you enter to tune your gear ratio and the accuracy of the DSC alignment. If someone moves the scope by accident, no problem, it can go back in few seconds.



Obviously, this solution is really great. The speed is really impressive. As the 32" is not that small, I have not use the max speed of the cat. It slewes at about 4degrees currently on azimuth. Other great point, the noise is incredibly low. During GOTO, you can hear it of course and I rather prefer that because people know they got to move This noise is by far much smaller than the solution we find on most SC and while tracking you simply don't hear it. What a pleasure to be under the star and don't have to use ear protection

ServoCat front panel


Input data in the servo cat

All datas are stored in the Cat. To upload this numbers, you got to use a small program which is on the CD-Rom. With that program, you can tune the ratio of the AZ and Alt drive, choose  6 speeds to move the scope, choose acceleration/deceleration time in seconds, and choose backlash correction. It's really easy to do. You use a computer for this operation but once you got the good number, you no longer need it.



How to use it

First you align the DSC. For the argo navis, don't forget to use the fix alt ref menu. Second, you engage the AZ and Alt drive. Third you choose your target in the database and you press the "GOTO" button on the handpad,  the scope slewes to the object. If it's not in the field of view, most of the time it's due to a lack of accuracy of the alignment.

For safety reason, the hand pad must be close to the scope while slewing. The Cat check the hand pad feedback and if it doesn't receive anything, it stopped. Also, in case you want to stop a GOTO because you see that the ladder is on the way or other problem, simply depress 3 of the direction buttons on the hand pad.


Electrical power


Electrical power

An other great point for the cat, it's not exactly a cat, it's a Camel,  his power consumption is really low. I use a 12 Ah rechargeable battery and I can observe at least a  full night without any problem even with numerous "GOTO".


It's important to understand that the accuracy of the system depends of two parameters : the alignment accuracy of the DSC and the accuracy of the gear ratio. So, when you have finished the whole installation, spend some time to tune the numbers.

This kind of motorisation can use friction or cable. The friction drive is easier to make but is heavily dependant, for the altitude drive, of the good OTA balance. It can be interesting to spend more time and use wires if possible. It avoids most of the slipping problem. That give a smoother tracking. This solution is used by Gary when he installs the Cat on Obsessions scopes.


Servocat rear panel



The Cat is not "frozen in the time", when necessary, there is evolution. For example, a derotator is planed in the future. It's quite easy to change the "bios" of the electronic box.



Service quality

The service provided by Gary is great. If you got a problem with the system, you are not lost in the dark, I got one of the very first unit and all the small problems have been corrected. Other problems mostly came from error of my own.

Bottom line, I love this system  !!!