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Improving the CG-5 Equatorial Mount

Right Ascension Axis, Part 2


CG-5 INFORMATION
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Right Ascension Axis
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RA Shaft
When the RA shaft is withdrawn from the RA housing, check to see whether the large plastic washer has adhered to the bottom of the silver worm gear or whether it is still inside the RA housing.

Slide the RA worm gear from the RA shaft. Be sure to note which plastic washer goes on which end of the gear; the washers have different cross sections. Don't lose track of the small plastic button in the RA lock mechanism, which is on the inside of the upper part of the RA shaft. See the declination section for a reminder of where this plastic button is located.

The RA worm gear can be difficult to remove from the housing, being virtually glued in place by the sticky grease. This seems to be a problem especially with newer versions of the mount. CG-5 owner Ed Calvert suggests using a hair drier to heat the R.A assembly. With his CG-5, this caused the factory grease to soften, and the RA gear was easily removed.

  RA worm gear

RA Fix-up
Note: Do not attempt to "dry fit" the worm gear on the RA shaft without some kind of lubrication. Keep the inside of the worm gear lubricated when checking the fit. Otherwise, it can easily bind on the shaft and be very difficult to remove.

Clean, smooth, polish, and re-grease the RA assembly as you did the Dec components. Pay lots of attention to smoothing all bearing surfaces and removing rough spots from the two large plastic washers on either end of the RA worm gear. Use your sharpening stone and Crocus cloth as necessary.

Take care to grease all bearing surfaces, being especially careful to lubricate the portion of the RA housing into which the bottom of the worm gear seats. Grease the entire inside of the worm gear before slipping it over the RA shaft.

On the outside of the worm gear, you need grease on the gear teeth only. Most of the outside of the worm gear does not bear on anything and so needs no grease. The bottom end of the gear rests in a portion of the RA housing which must be greased as described above.

Put grease on both sides of each plastic washer. When reassembling the RA mechanism, be sure to replace all of the washers in their correct locations.

The RA axis of my first CG-5 seems to be inherently tighter than the Dec axis. Therefore, I tightened the ring nut only enough to prevent the RA shaft from moving up and down in the housing. After several months' use, the RA axis has NOT become noticeably looser.

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The RA axis of my second CG-5 is inherently looser. I'll probably need to tighten it up after a few months of use.

As with the Dec axis, I devoted much time to adjusting the worm assembly, making it as loose and easy to turn as possible without allowing the RA shaft to wobble. I was successful in that I can turn the RA worm with my thumb and index finger without using the knob. Refer to the adjustment instructions in the Dec section.

Wrapping It Up
The mount moves quite freely in both axes now, whereas it was very stiff before I cleaned, smoothed, and re-greased it. It's much easier to smoothly slew the scope by hand now; it was sometimes jerky before. And it is much easier to balance the scope properly.

I have added an inexpensive drive motor to the RA axis, and the mount tracks very well. With a Celestron C5 Schmidt-Cassegrain telescope, the CG-5 is just right for visual observing.

If you have questions, please e-mail them, and I will try to help.

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