Hi,

In visual and film photography through telescopes on equatorial
drives, the old RA drive system might use commercial gears (Boston
probably) and a synchronous drive motor like a BODINE or a HURST. This
would be controlled using a variable frequency controller.

This was used in conjunction with a DEC drive with another synchronous
motor and gears.

A contol box, held in the hand with 4 buttons and a reostate type
device for setting the system to a siderial rate would be used.

The user kept the target or a near by star in the cross hairs of a
guide scope or off-axis guiding device.

I have been told that this configuration is insufficiently accurate
for CCD photography and a periodic correction via a computer driven RA
drive is needed to compensate for periodic errors in the RA worm gear
and other associated gears.

Is this correct ?

If so, when I buy my next telescope with which I plan to do CCD
photography, what do I need to look for and ask for in the product I
buy.

I will be getting something in the 11 to 14 inch aperture range. It
will be on a permanent mount on a concrete pier and isolated from the
concrete pad upon which I will be walking.

My need for this info is not terribly immediate. The purchase will be
in a few years for my retirement home in UTAH but I figured getting
some heads up info on the issue now would not be a bad idea.

Any and all comments will be appreciated.

Sincerely,

Jim Klein
James E. Klein


Engineering Calculations
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