Polar Alignment
Definition:
In order for the telescope to track the stars, you must meet two criteria. First, you need a drive motor that moves at the same rate as the stars. The Celestron
Polar alignment is the process by which the telescope’s axis of rotation (called the polar axis) is aligned (made parallel) with the Earth’s axis of rotation. Once aligned, a telescope with a clock drive will track the stars as they move across the sky. The result is that objects observed through the telescope appear stationary (i.e., they will not drift out of the field of view). If not using the clock drive, all objects in the sky (day or night) will slowly drift out of the field. This motion is caused by the Earth’s rotation. Even if you are not using the clock drive, polar alignment is still desirable since it will reduce the number of corrections needed to follow an object and limit all corrections to one axis (R.A.). There are several methods of polar alignment, all of which work on a similar principle, but performed somewhat differently. Each method is consid- ered separately, beginning with the easier methods and working to the more difficult.
Although there are several methods mentioned here, you will never use all of them during one particular observing session. Instead, you may use only one if it is a casual observing session. Or, you may use two methods, one for rough alignment followed by a more accurate method if you plan on doing astrophotography.
The polar axis is the axis around which the telescope rotates when moved in right ascension. This axis points the same direction even when the telescope moves in right ascension.
Figure
30 • Astronomy Basics
