Equatorial Mount - Meade EXT90 Instruction Manual

viewed through a telescope such as an ETX, this
motion is rapid indeed. If the motor drive has not been
engaged, celestial objects viewed in the telescope
eyepiece drift entirely out of the field of view in 15 to 60
seconds, depending on the magnification employed.
However, by mounting your telescope and turning on
the motor drive, you can counteract the drift of objects
in the eyepiece. The two basic types of mounting
are: altazimuth (alt/az) and equatorial. For many ETX
owners, it will not be necessary to equatorially mount
the telescope; alt/az mounting will suffice. The AutoStar
Controller allows the telescope to be mounted in the
altazimuth (alt/az) mode for most observing purposes.
See Easy (TWO-STAR) Align, page 11, for more
information.
However, owners who wish to perform astro-
photography will find equatorial mounting indispensable
to their needs.

Equatorial Mount

Equatorial mounting lines up the telescope's polar axis
with the North Celestial Pole (or the South Celestial
Pole if observing in the southern hemisphere).
When using an equatorially mounted telescope,
tracking (following) celestial objects is possible by
turning on your ETX telescope's motor drive. The motor
counteracts the Earth's rotation and keeps objects in
the field of view of the eyepiece for hands-off tracking.
Equatorial Mounting Procedure
1. Assemble the tripod as described in Step #2 of
Getting Started on page 5.
2. Loosen the latitude control latch (Fig. 19) and lift
up the tilt-plate so that you can easily access the
underside of the plate. Relock the latitude control latch,
so the assembly doesn't slip while you are attaching
the telescope.
3. Turn the tripod, so that the face of the tilt-plate points
North (Figs. 20). If you attach the telescope to the
tripod indoors, be sure to orient the face of the tilt-plate
to point North after moving the telescope outdoors.
Equivalently, point the tripod leg (Fig. 20) North. This
is the leg opposite from the latitude control bar (Fig.
18) .
4. Line up the mounting hole on the base of the telescope
so the computer control panel faces westward. Thread
both attachment knobs into the base of the telescope.
Tighten to "firm-feel"
Figure 18: Attach Telescope to Tripod
Tighten to a firm-feel only.
5. Determine the latitude of your observing location
from a road map, atlas or the Latitude Chart for Major
Cities of the World, page 54. Loosen the latitude control
latch (Fig. 19) and adjust the latitude control bar (Fig.
18) so that your observing site's latitude is just visible
above the flat surface of the tripod head. Retighten the
latch.
Figure 19: Set latitude
6. If you have not already done so orient the tripod leg
(Fig. 20) so that it is pointing due North (if the location
of Polaris, the North Star, is known, point the telescope
directly at Polaris. Observers located in the Earth's
Southern Hemisphere must point the telescope due
South).
7. The telescope is now equatorially mounted; the
tripod must not be moved or else the alignment will
be lost. Instead, use one of the following methods to
move the telescope's optical tube to a desired celestial
object.
(a) Loosen the vertical and/or horizontal locks (Pg 13,
Fig. 3, 6 and 9) to permit the optical tube to be freely
moved manually. Tighten the locks once you center on
the object.
(b) With the horizontal and vertical locks in their
Latitude control bar
Latitude control latch
1