Orion 52083 - Manual (Page 39)

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an extremely accurate polar alignment. Unfortunately it is very time consum-
ing, since the drift of a star over time must be observed. The basic idea is to
let the telescope mount track while watching a star to see which way the star
drifts. Note the direction of the drift, and correct by moving the mount in the
appropriate direction.
To perform the drift method of polar alignment:
1. Do a rough polar alignment by pointing the R.A. axis of the mount at Polaris
(the North Star).
2. Find a bright star near the meridian (the imaginary line running north-to-
south through zenith) and near the celestial equator (zero degrees declina-
tion). Point the telescope at this star, and center it in an illuminated reticle
eyepiece (available from Orion). If you don’t have an illuminated reticle
eyepiece, use your highest- magnification eyepiece.
3. Determine which way is north and south in the eyepiece by moving the
telescope tube slightly north and south.
4. Now, let the mount’s motor drive run for about five minutes. The star will
begin to drift north or south. Ignore any east-to-west movement.
5. If the star drifts north, the telescope mount is pointing too far west. If the
star drifts south, the telescope mount is pointing too far east. Determine
which way the star drifted and make the appropriate correction to the azi-
muth position of the mount. Rotate the entire mount (and tripod) slightly
east or west as needed or use the azimuth adjustment knobs (if your mount
has them) to make fine adjustments to the mount’s position.
6. Next, point the telescope at a bright star near the eastern horizon and near
the celestial equator (Dec. = 0).
7. Let the telescope track for at least five minutes, and the star should begin
to drift north or south.
8. If the star drifts south, the telescope mount is pointed too low. If the star
drifts north the telescope mount is pointed too high. Observe the drift and
make the appropriate correction to the mount’s altitude (or latitude); most
mounts have some sort of fine adjustment for this.
Repeat the entire procedure until the star does not drift significantly north or
south in the eyepiece. When this is accomplished, you are very accurately
polar aligned, and should be able to produce good (unguided) images of up
to several minutes long, assuming the mount’s drives track well with little
periodic error.
Focusing
One of the hardest things to do in imaging is achieving good focus. You can
simply watch the computer screen to focus (Focus in the Camera Control
Window), but you can focus “by the numbers” on a bright star to get the best
focus possible. To do this: