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Our Equatorial Platform is now completed and we have used it several times. The experience compared to untracked is the proverbial chalk and cheese. Our speed calculations must have been very close to correct as with only average polar alignment objects stay in the FOV for a considerable length of time. We are very happy.
However, there is a weakness in the design which should have been obvious from the onset. The objects stay in the FOV but actually move around (literally round) within the FOV. This is caused by actually rotating the threaded rod whereas other designs have the rod fixed and rotate a gear that either lifts or lowers the rod. The rod run out in the lathe is within a few thou, however, no matter what coupling (we are now on the third iteration) there is far more run out at the end of the 200mm of rod when connected to the stepping motor. The last coupling as pictured is machined from mild steel and clamps rather than having a set screw on the flat of the stepping motor shaft. This is the best so far but still not perfect. The run out of the rod highlights the fact that the hinges will allow side to side movement. The periodic movement limits the length of exposure time considerably so we are presently re-engineering the stepping motor mount to include a threaded gear and fixing the threaded rod at the top end. Hopefully this will be a great improvement.
Peter & Clare
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