From: "Dave Pitou" 
To: 
Reply-To: "Dave Pitou" 


Hi Byron,

I've tried the classical drift allignment method, but found it real slow.
15 or 20 years ago I developed a method that's much faster and has proven
accurate enough for prime focus ccd imaging on a 20" newt.

The basic idea is that there is a triangular pattern of stars surrounding
the pole that will be in a certain position in the eyepiece field when the
telescope is centered on the pole (a 20mm Nagler on my scope works best,
but it'll probably be different on your scope). In order to allign an
equitorial mount you rotate the fork horizontal and move the azimuth
adjustment until the three star pattern just fits in the FOV. Then the fork
is rotated to verticle and the altitude adjustment is made. What you are
doing is using the altitude (or azimuth) as one axis of rotation and the
Dec axis as the other in order to place the star pattern in its correct
position. The three stars are SAO 3788 at RA 21:05:57 Dec 89:46:59, SAO 438
at RA 04:50:45 Dec 89:38:11, and SAO 1157 at RA 09:51:19 Dec 89:33:32. The
correct position of the stars in the FOV is best gotten from an atlas or
The Sky by centering the eyepiece field on the true pole (the pole used to
be a little better centered in the triangular pattern, but the pole moves
even over 15 years!). The final test is to rotate the scope about the polar
axis while looking in the eyepiece and watch the triangular pattern of
stars rotate about the pole.

With some practice the whole allignment takes 10 or 15 minutes, and the
accuracy is within a few minutes of arc.

Dave


----- Original Message -----
From: "Byron Ader" 
To: 
Sent: Thursday, May 29, 2003 10:39 AM Subject: ATM Polar Alignment


>
> I believe I can read and find this out in Bell's book but I figured I
would
> just ask since it is on my mind.  Do guys know of a quick and easy way to
> get accurate polar alignment with a equatorial fork mount?
>

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