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Mt Pleasant 14m

Ariel view of the 14m showing construction of the Astronomical Society of Tasmania observatory facilities to the right.

The 14m telescope located at the Mt Pleasant observatory is currently undergoing structural repairs as well as motor and receiver installation. This wiki documents the ongoing status of the refurbishment.

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Observatory Specific Documentation

Work Required

Structural Repair

The 14m telescope at the Mt Pleasant observatory, since being altered for higher frequency measurements, has been out of service. Initially, the intention was to wire the motors and set up the system for controlling them. However, inspection of the telescope’s frame revealed large amounts of damage; likely due to the dish’s continued rocking. The main points of concern were certain joints on the structure which were cracking from stress and torque, as well as the severely cracked bearing and housing.

It was decided that returning the 14m telescope to working order would require replacement bearings and re-welding of joints, for which the dish must be removed. Prior to removing the approximately 2 tonne dish, the two counterweights were strapped to the dish and winched to the ground. The dish was then tied to the structure for safety. A wooden platform was assembled in a nearby open area in preparation for placing the dish on the ground; multiple concrete blocks were placed around the platform for the dish to be tied to once down. The dish was removed by means of a crane, with four ropes run through the receiver structure and tied to equally spaced joints on the dish’s frame.

The cracks have been welded and reinforcing material added for strength. New bearings have been fitted to the elevation axis. The dish is back on the pedestal.

Motor Installation
The 14m telescope requires four motors; two for the elevation control and two for the azimuth. The two motors for elevation were on the telescope and had become quite weathered, so they were cleaned and brought inside for testing along with the two azimuth motors. Each of the four motors required an encoder fit to the shaft to measure the degree of rotation and send said information back to the control system. Two of the four encoders were the wrong size for the motors, thus requiring a custom adaptor to be made. After adapting and fitting the encoders, the four motors’ encoders, 3-phase supply and brakes were wired and the motors tested. All motors, encoders and brakes were found to be in working order.

Elevation #1 green encoder cable appears broken, will need to be pulled and fixed or replaced. Elevation #2 encoder cable tested and working.

Receiver Installation
The receiver is currently on the bench for testing. Limit switches require pull-up resistors to draw more current to wet the contacts to stop surface corrosion.

Network

Blue ethernet cable running underground and down cable tray to 14m is cut in several places, needs replacing and securing.

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All Pictures

Structural

Motor

Receiver
insert pictures here

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History

Originally an equatorial telescope installed near the Hobart airport in the mid 1960s. In the 1980s the telescope was reconstructed at the Mt Pleasant observatory, along with a new base structure and azimuth control.

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