Re: ATM Adjusting RA Tracking Rate Question

["Al Klayton" <aklayton@pcisys.net>]

Nils,
Thanks for the response.
Gerald North, in his book Advanced Amateur Astronomy (Cambridge), says....
an altitude error in the polar axis produces an East-West drift which is
greatest for objects near the meridian. An azimuth polar axis error produces
an East-West drift that is greatest for an object at 6h East or West of the
meridian. ...
So, my approach has been to do the best polar alignment I can (drift
method), then set the RA rate by tracking a star, then going back and doing
another polar alignment, then re-adjusting the RA rate again by star
tracking, then ..... and so on.  I was hopeful this going in circles would
accomplish something.  However, I find that what seems to be an excellent RA
rate one time, is a bit off the next (sometimes slow, sometimes fast).
Perhaps I'm just seeing the "natural" variability that is inherent in my
system e.g., the surplus Hurst stepper motors I'm using have a 300:1
reduction gearbox that I'm sure introduces some variable error, I just don't
know how much.  Bottom line is the table can typically keep an object within
about a 0.25 deg FOV over the 75 minutes of tracking provided before table
reset, but the "direction" of the error is not always the same.
Al

----- Original Message -----
From: Nils Olof Carlin <nilsolof.carlin@telia.com>
To: Al Klayton <aklayton@pcisys.net>; <atm@shore.net>
Sent: Sunday, July 18, 1999 9:28 AM
Subject: SV: ATM Adjusting RA Tracking Rate Question


> Al Klayton wrote:
>
> >I'm trying to accurately adjust the RA tracking rate on an equatorial
table
> >I have built by looking for East - West drift using a star near the
> >celestial equator.  But to do this requires an accurate polar alignment
> >since poor polar alignment shows up as East - West star drift.
>
> If you use a star at or near the meridian, the azimuth error in polar
alignment should show up as a North-South drift. If you keep this low by
turning the table base, the East-West error should reflect the error in
tracking rate.
>
> Nils Olof
>
>
>