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Subject: [M]: 1.50 arcsec/minute per 0.1 Hz
From: J HOPPER
Reply To: mapug@shore.net
Date: bogus date

Richard Davis wrote (in response to Paul Goelz):

>Well, Paul, the key to this susggestion is knowing what the
relationship
>is between the frequency used to control the RA drive and the RA
rate of
>drive in arcseconds. Would a change from 60.1 to 60.0 Hz produce a
>change in RA drive rate of 0.5 arcsec per minute, or 5.0 arcsec per
>minute, or whatever. These changes may be in the range needed to
>compensate for the persistent RA drift that may be otherwise
unavoidable
>when the SMART DRIVE is turned on.

This is a fairly easy calculation to do.
The answer is 1.50 arcsec/minute per 0.1 Hz change in frequency.

Here it is:
One revolution per day at 60.0 Hz.
One revolution = 360 degrees * 60 arcmin/degree * 60 arcsec/arcmin =
1,296,000 arcsec
One day = 1440 minutes

1,296,000 arcsec / (1440 minutes * 60.0 Hz ) = 15.000 arcsec/minute
per Hz

Note that to drive at sidereal rate would require 60.0 * (86,400/86,
164) = 60.164 Hz.
(Assumes one rev per 23 hours 56 minutes 4 seconds)

Perhaps Meade has programmed the controller to interpret a setting of
60.1 as being 60.164
if you guys truly get no drift at the 60.1 Hz setting.

The alternative is nastier, that the drive is actually running one
rev per sidereal day
at a true 60.1 Hz. In that case, the above calcs are slightly off,
but the result
would be neglibly different at 1.5016 arcsec/minute per 0.1 Hz.

In either case (1.5000 or 1.5016) the answer can be correctly stated
as 1.50

John Hopper
jhopper@prodigy.com
Temporarily LX200-less awaiting observatory with LX300 ;-)