GOTO Telescope Drive System with Servomotors


September 2001, I decided to replace my telescope's motorization. At first, I looked at commercial systems, but I found none that had everything that I wanted. So I decided to design and build my own system from scratch (I started from T. TAKI's alignment algorythm). I worked about 6 months on the software and the hardware. First field tests were done last June.


Here is the list of things I wanted to change in the new system:

1. Reduce stepper motors noise
Solution: Install servomotors
These motors are dead silent when tracking. Some noise is heard when slewing to an object, but the level is acceptable.

2. Increase slew speed (was 1.3 deg/s)
Solution: Install servomotors
The system can now slew at nearly 7 degrees per second. This is totally awesome!

3. Get ride of the cable mess
Solution: Design a system with the minimum number of cables
Except for the batteries, there is only one cable remaining: the secondary cage cable, which is captive in a truss.

4. Lower power consummation
Solution: Remove the need of a laptop, which is the biggest power eater
Laptop is no longer required. On the same batteries, expected run time jumped from 8 to more than 28 hours. That's great for a 2-3 nights in a row!

5. Replace current electronics with something more robust
Solution: Create a new control system and make it easy to replace
In the event of an electronic problem, the system can be replaced with a spare in only a few seconds. No electronics is permanently installed in the telescope.

6. Reduce setup time
Solution: "Clean" the telescope.
Many items were removed: laptop, laptop tray, DSC for encoders' feedback, as many cables possible, etc. The telescope setup time has been reduced by at least 5-7 minutes. If you compare to a dob without any electronics, the only additional things that I have to do are:
  • Install batteries
  • Install ALT encoder arm
  • Connect secondary cage cable
  • Do a 2 stars alignment

7. Add observation logging and more features
Solution: Create a system that can grow with the needs
The basic GOTO system is now working. This system now gives me the possibility to build my dream telescope computer system. This will allow customizing the system and adding many features that will be useful. For example, when the electronic boards were created, many functions were built in. But, I haven't programmed the system to use them yet. This will be done next winter.



The updated telescope, can you see the difference?

Old setup photo.
Compare the above to the new setup. Note all the items that were removed. And without losing any capability...
Viewed from the other side.