Celestron C8-S - Manual (Page 32)

32
Latitude Scales
The easiest way to polar align a telescope is with a latitude scale. Unlike other methods that require you to
find the celestial pole by identifying certain stars near it, this method works off of a known constant to
determine how high the polar axis should be pointed. The Advanced Series mount can be adjusted from 25
to 60 degrees (see figure 5-3).
The constant, mentioned above, 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 (i.e., 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. You
would have to travel 70 miles north or south to change your latitude by one degree. 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 is 34° above the
northern horizon. All a 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:
1. Make sure the polar axis of the mount is pointing due north. Use a landmark that you know faces north.
2. Level the tripod. There is a bubble level built into the mount for this purpose.
NOTE: Leveling the tripod is only necessary if using this method of polar alignment. Perfect polar
alignment is still possible using other methods described later in this manual without leveling the tripod.
3. Adjust the mount in altitude until the latitude indicator points to your latitude. Moving the mount affects
the angle the polar axis is pointing. For specific information on adjusting the equatorial mount, please see
the section “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. It will also be accurate enough for short exposure prime focus planetary photography (a
couple of seconds) and short exposure piggyback astrophotography (a couple of minutes).
Pointing at Polaris
This method utilizes Polaris as a guidepost to the celestial pole. Since Polaris is less than a degree from the
celestial pole, you can simply point the polar axis of your telescope at Polaris. Although this is by no
means perfect alignment, it does get you within one degree. Unlike the previous method, this must be done
in the dark when Polaris is visible.
1. Set the telescope up so that the polar axis is pointing north.
2. Loosen the DEC clutch knob and move the telescope so that the tube is parallel to the polar axis. When
this is done, the declination setting circle will read +90°. If the declination setting circle is not aligned,
move the telescope so that the tube is parallel to the polar axis.
3. Adjust the mount in altitude and/or azimuth until Polaris is in the field of view of the finder.
Figure 5-3
Latitude
Scale