10
3. Adjust the mount in altitude and/or azimuth until Polaris is in the field of view of the finder.
4. Center Polaris in the field of the telescope using the fine adjustment controls on the mount.
Remember, while Polar aligning, do NOT move the telescope in R.A. or DEC. You do not want to move the telescope itself, but the
polar axis. The telescope is used simply to see where the polar axis is pointing.
Like the previous method, this gets you close to the pole but not directly on it. The following methods help improve your accuracy for
more serious observations and photography.
Finding the North Celestial Pole
In each hemisphere, there is a point in the sky around which all the other stars appear to rotate. These points are called the celestial poles
and are named for the hemisphere in which they reside. For example, in the northern hemisphere all stars move around the north celestial
pole. When the telescope's polar axis is pointed at the celestial pole, it is parallel to the Earth's rotational
axis.
Many methods of polar alignment require that you know how to find the celestial pole by identifying stars
in the area. For those in the northern hemisphere, finding the celestial pole is not too difficult.
Fortunately, we have a naked eye star less than a degree away. This star, Polaris, is the end star in the
handle of the Little Dipper. Since the Little Dipper (technically called Ursa Minor) is not one of the
brightest constellations in the sky, it may be difficult to locate from urban areas. If this is the case, use
the two end stars in the bowl of the Big Dipper (the pointer stars). Draw an imaginary line through them
toward the Little Dipper. They point to Polaris (see Figure 12). The position of the Big Dipper changes
during the year and throughout the course of the night (see Figure 11). When the Big Dipper is low in the
sky (i.e., near the horizon), it may be difficult to locate. During these times, look for Cassiopeia (see
Figure 12). Observers in the southern hemisphere are not as fortunate as those in the northern hemisphere.
The stars around the south celestial pole are not nearly as bright as those around the north. The closest
star that is relatively bright is Sigma Octantis. This star is just within naked eye limit (magnitude 5.5) and
lies about 59 arc minutes from the pole.
The north celestial pole is the point in the northern hemisphere around which all
stars appear to rotate. The counterpart in the southern hemisphere is referred to as the south celestial pole.
Definition
Figure 11 - The position of
the Big Dipper changes
throughout the year and the
night.
Figure 10- Aligning the Equatorial mount to the polar axis of the Earth.
