Meade 2045 - Lining Up With The Celestial Pole

appear to be placed.
The Poles of the celestial coordinate system are defined as those two points where the Earth’s rotational
axis, if extended to infinity North and South, intersect the celestial sphere. Thus, tHe North Celestial Pole
is that point in the sky where an extension of the Earth’s axis through the North Pole intersects the
celestial sphere. In fact, this point in the sky is located near the North Star, Polaris.
On the surface of the Earth, "lines of longitude” are drawn between the North and South Poles. Similarly,
"lines of latitude" are drawn in an East-West direction, parallel to the Earth’s equator. The celestial
equator is simply a projection of the Earth’s equator onto the celestial sphere. Just as on the surface of
the Earth, imaginary lines have been drawn on the celestial sphere to form a coordinate grid. Celestial
object positions are mapped on this grid in the same manner as positions on the Earth’s surface are
specified by their latitude and longitude.
The celestial equivalent to Earth latitude is called "Declination,” or simply "Dec.," and is measured in
degrees, minutes and seconds North ("+") or South of the celestial equator. Thus any point on the
celestial equator (which passes, for example, through the constellations Orion, Virgo and Aquarius) is
specified as having 0°0 min 0 sec 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 o hr o m i n O sec up to (but not including)
24 hr o m i n o sec . Thus there are 24 primary lines of R.A., located at 15° intervals along the celestial equator.
Objects located further and further East of the prime (o hr o m , n O sec ) 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
greatly simplified. The setting circles of the Modei 2045 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.
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, describing concentric circles with the Pole at the
center. By lining up with the telescope’s polar axis with the North Celestial Pole (or, for observers located
in the Earth’s Southern Hemisphere, with the South Celestial Pole), astronomical objects may be
followed, or tracked, simply by moving the telescope about one axis, the polar axis. In the case of the
Meade Model 2045, this tracking may be accomplished automatically with the electric motor drive.
For the purposes of casual visual telescopic observations, 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’s
motor drive will track accurately and keep objects in the telescopic field of view for perhaps 20 to 30
minutes.
To line up the telescope with the North Celestial Pole, follow this procedure:
1. Attach the 3 tripod legs to the telescope, as shown in Fig. 1. Note that one leg is adjustable in length.
This leg should be threaded into the central hole on the underside of the drive base.
2. The polar axis of the telescope is an imaginary line running through the adjustable tripod leg, up through
the center of the drive base, and up between and parallel to the two fork arms. The long arrow in Fig. 2
indicates the polar axis. (It is around this axis that the telescope turns in Right Ascension). In Fig. 2, the
telescope is oriented so that the main optical tube is also aligned with the polar axis. With the telescope
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