DFM Engineering 1.3 m astronomical optical telescope Operation and maintenance manual

Below you will find brief information for astronomical optical telescope 1.3 m. The DFM 1.3 Meter is an equatorial fork mounted Cassegrain telescope. Its drives are two stages of friction drive (a large disk driven by a small roller) driven by a stepping servomotor through a timing belt and pulley stage. The absolute 25 bit HA and DEC encoders are on-axis. The focus motion is provided by a stepper motor driven secondary mirror. Focus position is recorded with a belt driven potentiometer and an incremental optical encoder. Secondary mirror collimation is accomplished with 4 motorized and LVDT absolutely encoded x-y stages. These stages allow secondary translation and tilt in both X and Y, commanded and displayed from the control system computer. The primary mirror axial support consists of 36 counterweighted lever back supports and thermally compensated defining points on the mirror OD. The primary mirror radial support system consists of 16 passive radial counterweights, and 4 thermally compensated radial hark points. Mirror doors protect the primary mirror and a plate attached to one of the doors acts as a dust cover for the primary light baffle tube. A full mechanical drawing package of the telescope is provided.

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DFM Engineering 1.3 m Astronomical Telescope Operation and Maintenance Manual | Manualzz

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Key features

  • Equatorial fork mounted Cassegrain telescope
  • Two stages of friction drive
  • Stepping servomotor
  • Absolute 25 bit HA and DEC encoders
  • PC controlled
  • Mercury limit switch assembly

Frequently asked questions

The declination bearing axial preload is set to equal the weight of the tube assembly. Loosen the Dec bearing lock-nut approximately three turns. Set up a magnetic base and dial indicator to verify the motion between the fork end and the west bearing housing. Loosen the four 3/8 allen cap screws securing the bearing housing to the fork two turns each. Use the set screws to move the bearing housing outboard the distance stamped on the housing and then tighten the 3/8 allen cap screws to the torque listed on the telescope assembly drawing. Finally, preload the bearings by tightening the bearing lock-nut.

It is important to balance the telescope to optimize performance, increase instrument life, and for safety. Both axes of the telescope may be balanced by using the amp-meters on the front panel of the motor driver chassis. The meters read +3 and - 3 amps full scale. Use the hand paddle to see that the same current is required to slew in both directions for each axis. Adjust the counterweights until balance is achieved. Counterweights provided include weights for the bottom of the primary mirror cell and motorized weights for Declination. RA balance should not need adjustment unless an asymmetrical instrument is used. If RA does need adjustment, the sliding fork weight can be adjusted. A better DEC balance may be achieved by releasing the primary drive roller and pulling on the mount with a spring scale and adjusting counterweights.

The RA primary roller normal force is provided by gravity and requires no adjustment. The DEC primary roller normal force is set by turning a 3/8-24 screw in the DEC drive that pushes the primary roller into the disc with a spring. To adjust normal force: 1. Loosen the DEC normal force screw until the tube assembly moves freely. 2. Tighten the screw until a 5-8 pound pull on the top of the tube assembly perpendicular to the DEC axis does not cause rotation.
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