Misti Mountain Observatory - Astronomy Pages
Star Clusters
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7" Refractor

32" RC Telescope - Motor Drives Detail
This is a view of the declination drive. The large brass wheel is a 15" Byers gear with 360 teeth. The smaller concentric brass wheel is used as a clutch to adjust the pressure required to move the telescope independently of the motor drive. The ring of screws near the axis are used to adjust the tension of this clutch.

The aluminum cylinder at the right is the declination axis, with the counterweights out of the photo to the right.

This entire assembly is enclosed with a clear plexiglass cover in operation (removed for these photos) to maintain a dust free environment for the gear assemblies.

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This is a closeup of the declination drive worm-gear and motor assembly. The worm gear (at lower left) is covered with a liberal coating of axle grease to reduce friction and wear on the gears.

The drive motor is the black box at the right, and is a 500-step per revolution stepper motor.

Connecting the stepper motor to the worm gear is a large-diameter stainless steel flexible coupling, seen at the lower center, with helical grooves cut around it's circumference. This coupling helps relieve potential strain caused by minor misalignment between the motor and worm gear, also helps to dampen any impulses caused by the stepper motor action.

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This is a closeup of the RA (polar axis) drive mechanism. This drive uses an 18" Byers gear with 584 teeth.

The large black wire coming out of the RA axis is from the Dec drive motor, and is routed through the RA and Dec axes, coming out behind the brass drive gear in the above photos.

The RA drive motor (lower right) is the same as the Dec drive motor, except that it has a 50:1 reducing gearhead. This was a substitution I made to eliminate a residual "wobble" in high-power views of solar-system objects caused by an inherent short-period error in all micro-stepped stepper motors. In this telescope, this "wobble" amounted to about 1 arc-second, with a frequency of about 3 times per second. While this is less than the average seeing limit, the effect in a 1/2" eyepiece at 500 power was quite noticeable.

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