(which passes, for example, through the constellations Orion, Virgo and Aquarius) is specified as having
0°0'0" Declination. The Declination of the star Polaris, located very near the North Celestial Pole, is +89.2°.
The celestial equivalent to Earth longitude is called “Right Ascension,” or “R.A.” and is measured in hours,
minutes and seconds from an arbitrarily defined “zero” line of R.A. passing through the constellation
Pegasus. Right Ascension coordinates range from 0hr0min0sec up to (but not including) 24hr0min0sec.
Thus there are 24 primary lines of R.A., located at 15 degree intervals along the celestial equator. Objects
located further and further east of the prime (0h0m0s) Right Ascension grid line carry increasing R.A.
coordinates.
With all celestial objects therefore capable of being specified in position by their celestial coordinates of
Right Ascension and Declination, the task of finding objects (in particular, faint objects) in the telescope is
vastly simplified. The setting circles, R.A (27) and Dec. (28) of the Model 4500 telescope may be dialed, in
effect, to read the object coordinates and the object found without resorting to visual location techniques.
However, these setting circles may be used to advantage only if the telescope is first properly aligned with
the North Celestial Pole.
D. Lining Up with the Celestial Pole
Objects in the sky appear to revolve around the celestial pole. (Actually, celestial objects are essentially
“fixed,” and their apparent motion is caused by the Earth’s axial rotation). During any 24 hour period, stars
make one complete revolution about the pole, making concentric circles with the pole at the center. By lining
up the telescope’s polar axis with the North Celestial Pole (or for observers located in Earth’s Southern
Hemisphere with the South Celestial Pole), astronomical objects may be followed, or tracked, by moving the
telescope about one axis, the polar axis.
If the telescope is reasonably well aligned with the pole,
therefore, very little use of the telescope’s Declination
flexible cable control is necessary and virtually all of the
required telescope tracking will be in Right Ascension. (If
the telescope were perfectly aligned with the pole, no
Declination tracking of stellar objects would be required).
For the purposes of casual visual telescopic obser-
vations, lining up the telescope’s polar axis to within a
degree or two of the pole is more than sufficient: with this
level of pointing accuracy, the telescope can track
accurately by slowly turning the telescope’s R.A. flexible
cable control and keep objects in the telescopic field of
view for perhaps 20 to 30 minutes.
To line up the Model 4500 with the pole, follow this procedure:
1) Release the Azimuth lock (30) of the Azimuth base (33), so that the entire telescope-with-mounting may
be rotated in a horizontal direction. Rotate the telescope until the polar axis (10) points due North. Use
a compass or locate Polaris, the North Star (see Fig. 3), as an accurate reference for due North.
2) Level the mount, if necessary, by adjusting the heights of the three tripod legs.
3) Determine the latitude of your observing location by checking a road map or atlas. Release the latitude
lock (9) and tilt the telescope mount with the latitude adjustment knob (11) so that the pointer indicates
the correct latitude of your viewing location on the latitude scale (29). Re-tighten the latitude lock (9).
4) If steps (1) - (3) above were performed with reasonable accuracy, your telescope is now sufficiently well-
aligned to the North Celestial Pole for visual observations.
Once the mount has been polar-aligned as described above, the latitude angle need not be adjusted again,
unless you move to a different geographical location (i.e. a different latitude). The only polar alignment
procedure that need be done each time you use the telescope is to point the polar axis due North, as
described in step (1) above.
E. Using the Telescope
With the telescope assembled, balanced and polar aligned as described above, you are ready to begin
observations. Decide on an easy-to-find object such as the Moon, if it is visible, or a bright star to become
accustomed to the functions and operations of the telescope. For the best results during observations, follow
the suggestions below:
– 9 –
Polaris
Little Dipper
Big Dipper
Cassiopeia
Fig. 3: Finding Polaris