Retrofitting an Autostar for C8 Autoguiding Page

Project Background and Requirements

I had an unused Meade Autostar controller and 492 motors from my disassembled GoTo truss tube mount and decided to test if I could retrofit the Autostar motors to a C8 fork mount for autoguiding. I have seen several Autostar SCT conversions that involved removing the synchronous motors and permanently fitting the Autostar motors inside the drive base and bolting them to the forks. Since I wanted to keep my C8 in its original condition, there were a few restrictions on the project.
  1. The entire autoguider system must be removable and not permanently mounted to the C8 drive base
  2. The motor mounting system must not alter or damage the C8 in any manner  

Prototype 1

I mounted the Autostar motors to scraps of nylon cutting board; the nylon provided a solid surface that would not scratch the C8 drive base paint. I cut the nylon sections to tightly fit in between the forks (perpendicular to the RA axis) and to fit inside the recess on the outside of the wedge with the declination axis fine adjustment knob. The dec motor was attached to the outside of the fork by strong elastic bands; this gave a removable mounting system that didn't damage the original fork mount. For the RA drive system, I retained the small 60 tooth Meade worm wheel and added a section of M6 threaded rod attached to a plastic cup. I formed the inside of the cup to exactly fit over the RA adjustment knob by adding a few drops of thermoplastic from a hot glue gun and pressing it over the RA knob. For the declination axis, I fabricated a simple belt drive that fits over the declination axis fine adjustment knob. The prototype drive system is shown below.

C8 Autoguider Testing and Status

The basic design functioned very well. The Autostar motors could move the C8 about both axes and everything appeared fine until star tracking tests. The dec drive functioned satisfactorily, but the RA drive could not track fast enough. Unfortunately the 60:1 reduction from the Meade worm wheel, coupled with the reduction from the C8's RA gear, was just too great. The Autostar RA motor ran at full speed, but the gear reduction was just too large and the C8 tracked too slowly. I planned to remove the Meade worm wheel and redesign the RA drive train, but suddenly one of my Autostar motors stopped functioning. Since Meade has discontinued the 492 external motors, they are now difficult to find and becoming expensive. I decided not to go any farther with this project, since these motors are discontinued.