[ubique (Hugh)]

EDWARD R. BYERS WORM GEARS
Two Aluminum worm gears with matching worms 7.54 inch diameter, the centre hole is 5 inch.
For more than four decades Edward R. Byers Co., manufactured astronomical equipment for observatories, colleges, universities, NASA's Jet Propulsion Laboratory, Lockheed Martin and other clients.
Byers had a worldwide reputation for precision machining and high quality tracking telescope mounts. Its worm gear drives are among the most accurate ever created for astronomy. The accuracy of these gears is especially noticeable during long exposure astrophotography. Periodic error is almost nonexistent. The exceptional accuracy was achieved by Byers' precision machining and the design of the gears.
The items offered are Byers' 7.54 inch diameter aluminum worm wheels with 359 teeth.
Also included is the matching steel worm and bronze bearing assembly. The worm is machined to couple to a .18" (4.8mm) shaft.
These gears would be suitable for any telescope mount requiring high accuracy tracking ability.
PRICE $650 plus postage. Or $325 each but I would prefer not to separate them.
See -http://articles.adsabs.harvard.edu//full/2000IAPPP..79...17B/0000018.000.html
or Google Edward R. ByersCo.for more information.
PM me if you are interested.