Celestron C100ED-R, C80ED-R manual Finding the North Celestial Pole, Definition

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 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
Definition	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.

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.

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