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Figure 5-7
While the latitude scale
has a range of 0° to 90°,
going below 20 ? will
cause the counterweight
shaft to hit the tripod.
The Latitude Scale
The easiest way to polar align your C4.5 is with the latitude scale. Unlike
other methods that require you to find the celestial pole by identifying
certain stars near it, this method works using a known constant to determine
how high the polar axis should be pointed. The latitude scale for the C4.5 is
just above the azimuth adjustment screws (see figure 5-6).
The constant, mentioned previously, 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, or 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. 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 would be 34? above the northern horizon. Alla 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 using this
method:
1. Make sure the R.A. axis (also called the polar axis) is pointing due north.
Use a landmark that you know faces north, or you can use a magnetic
compass with the local correction for magnetic declination.
2. Make sure that the tripod is level.
3.
Move the equatorial head up or down until the latitude indicator points
to your latitude (see figure 5-7). For specific information on adjusting the
equatorial head, please see the section on "Adjusting the Mount."
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.
Astronomy Basics
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