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description of stellar motions also applies to the southern hemisphere except all stars south of the celestial equator move around the south
celestial pole.)
Latitude Scales
The easiest way to polar align a telescope is with a latitude scale. Unlike other methods that require you to find the celestial pole by
identifying certain stars near it, this method works off of a known constant to determine how high the polar axis should be pointed (see
figure 10).
The constant, mentioned above, is a relationship between your latitude and the angular distance the celestial pole is above the northern (or
southern) horizon; The angular distance from the northern horizon to the north celestial pole is always equal to your latitude. To illustrate
this, imagine that you are standing on the north pole, latitude +90°. The north celestial pole, which has a declination of +90°, would be
directly overhead (i.e., 90 above the horizon). Now, let’s say that you move one degree south — your latitude is now +89° and the
celestial pole is no longer directly overhead. It has moved one degree closer toward the northern horizon. This means the pole is now 89°
above the northern horizon. If you move one degree further south, the same thing happens again. You would have to travel 70 miles north
or south to change your latitude by one degree. As you can see from this example, the distance from the northern horizon to the celestial
pole is always equal to your latitude.
If you are observing from Los Angeles, which has a latitude of 34°, then the celestial pole is 34° above the northern horizon. All a latitude
scale does then is to point the polar axis of the telescope at the right elevation above the northern (or southern) horizon. To align your
telescope:
1. Make sure the polar axis of the mount is pointing due north. Use a landmark that you know faces north.
2. Adjust the mount in altitude until the latitude indicator points to your latitude. Moving the mount affects the angle the polar axis
is pointing.
This method can be done in daylight, thus eliminating the need to fumble around in the dark. Although this method does NOT put you
directly on the pole, it will limit the number of corrections you will make when tracking an object.
Pointing at Polaris
This method utilizes Polaris as a guidepost to the celestial pole. Since Polaris is less than a degree from the celestial pole, you can simply
point the polar axis of your telescope at Polaris. Although this is by no means perfect alignment, it does get you within one degree.
Unlike the previous method, this must be done in the dark when Polaris is visible.
1. Set the telescope up so that the polar axis is pointing north.
2. Loosen the DEC clutch knob and move the telescope so that the tube is parallel to the polar axis. When this is done, the declination setting
circle will read +90°. If the declination setting circle is not aligned, move the telescope so that the tube is parallel to the polar axis.
Figure 8 – Equatorial Head Firsctscope
70 (#21076)
Declination
Lock
R.A. Setting
Circle Lock
Latitude
Adjustment
Screws
Latitude
Locking
Screw
Latitude
Scale
Latitude Adjustment
Screws
Declination
Lock
Right
Ascension
Lock
Latitude
Scale
Figure 9 – Equatorial Head Firsctscope 90
(#21085)