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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.
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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 5-5). The position of the Big Dipper changes during the year and
throughout the course of the night (see Figure 5-4). 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 5-5). 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 5-4 The position of the
Big Dipper changes
throughout the year and the
night.
Figure 5-5
The two stars in the front of the bowl of the Big Dipper point to Polaris which is less
than one degree from the true (north) celestial pole. Cassiopeia, the “W” shaped
constellation, is on the opposite side of the pole from the Big Dipper. The North
Celestial Pole (N.C.P.) is marked by the “+” sign.