Finding The Pole - Celestron Ultima 11 Instruction Manual

Finding the 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.
Figure 4-4.
The position of the
Big Dipper changes
throughout the year
and throughout the
night.
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.
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
4-5). The position of the Big Dipper changes during the year and throughout
the course of the night (see figure 4-4). 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 4-5).
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. For more information about
stars around the south celestial pole, please consult a star atlas.
Figure 4-5
1
Ultima 9 /
4
and Ultima 11 Manual 33