We’re back!

It’s been a while since I posted here – just busy with saving Sugarloaf Ridge State Park from the budget buzzards. But we are back to work on the telescope, a wonderful palliative to dealing with bureaucracies.

On Sunday 1/8/12, Larry, Mark and I installed the shaft encoders. We used my design for the altitude mounting brackets and fabricated a bracket for the azimuth encoder on the spot out of 2”x1/8” aluminum plate. Larry’s azimuth pipe nut with brass tab welded to it was drilled out while the nut was on a similar pipe in a lathe. He added a set screw on the nut itself to lock it into place, and a set screw in the brass tab to lightly grip the encoder shaft.

After looking over the wiring needs with the new encoders both mounted above the base, we decided to move the controller and hand pad base station to the top of the base. We still needed to run three wires up through the pipe/shaft. There turned out to be insufficient space to get the wires with plugs through the nut with brass tab until we removed the nut and trimmed the plastic plugs to slip through. We validated that it all worked with the hand pad.

On Saturday, 1/14/12, Larry, Mark, Steve and I met and set up to do some testing of the telescope drive, now that we had all of the encoders in place. I’d spent the previous week updating Microsoft and anti-virus software on the desktop donated by Alan Loceff. We set up and connected the serial port to the controller, and began the process of syncing The Sky 6 to objects in the sky. Users of the 14-inch would have found the process familiar. We opened The Sky and Established a connection to the telescope. We found an object manually, using the handpad, and after searching for the object with a text search, hit the Sync button. Then we moved it by hand to another star and repeated. On our first slew move, the telescope moved a short distance and then stopped. After several repetitions that convinced us it wasn’t just bad luck, we retired to the tick management screen.

The SiTech team thoughtfully provided an application page that takes you through the tick calibration process on each axis, one at a time. You start by putting the telescope manually in a starting position (a known, measurable altitude or azimuth). You then let the telescope try to move to the test angle (90º). If it doesn’t get there, manually move the telescope to the test angle and sync. Then tell the scope to move back to the origin, and finally, sync one more time. It became obvious that the tick count per revolution was off by a factor of 5, the gear ratio of the new planetary gear box. Must’ve forgotten to add that factor into the configuration calculation. Once that was ironed out in both altitude and azimuth, we started on a test run. Halfway through the first slew, the azimuth drive stopped functioning. We could hear the motor spinning, but no motion. We adjusted the clutch, checked everything we could think of, but still no help.

Reluctantly, we removed the azimuth drive from the mount. It was nice that we thought about being able to remove the drive unit easily. Back home on the bench, I discovered we had ripped the control cable jack out of the circuit board.

Next time: tie wrap strain relief!

That probably explains the weird behavior. We’ve ordered a replacement jack and are patiently waiting for it to arrive so we can do the emergency surgery.


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