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University of Montreal - Mt. Megantic Observatory
Telescope Control System Installation


A new DFM Engineering Inc. Telescope Control System (TCS) was installed last week at Mt. Megantic Observatory in Quebec, Canada, for the University of Montreal.

The 63 inch aperture Perkin Elmer telescope had been in continuous use since 1977 and the control system electronics slowly became difficult to support.

The University of Montreal wanted to modernize the telescope by installing a computer controlled TCS along with new secondary drives, focus motor, focus encoding, the automation of dome control and the motorization and automation of the existing manual Perkin Elmer instrument rotator.

We removed the three motors and all secondary gearing from the RA and DEC drives, leaving the primary worm boats in place.

New timing belt pulleys were installed on one end of the worm shafts and a new optical incremental shaft encoder on the other. Two stages of timing belts and a single DC servo-motor per axis were installed.

The focus motor was replaced with a new DC servomotor and a precision potentiometer was installed to encode focus position. A dome encoder and encoder drive were installed along with controls to command the dome motors. The instrument rotator brakes and drive pinion were motorized and controlled from the TCS. The Perkin Elmer 5 degree mercury limits were wired to be the Horizon interlock for the new TCS. The Perkin Elmer 8 degree mercury limits were used as Approaching Limits for the new TCS. The Perkin Elmer primary worm de-mesh switches became inputs to the new TCS, canceling commands and limiting motion. All new wiring was done with low temperature cables.

After the new controls were installed, we tuned up the pointing model on both the East and West sides of the pier. Pointing was considered good enough when we achieved 10 arc seconds RMS. Tracking was tested, and the telescope tracked to 1.5 arc seconds unguided in one hour. We used “The Sky” by Software Bisque to command the telescope. The existing guider was quickly interfaced to the new TCS.

The university will now proceed with integration of the TCS into their Observatory Control System, which will control instrumentation and have internet access.