The Electronic Controller; Modes Of Operation; Using The Mode Screws; Electronic Controller Modes - Meade ETX-90EC Instruction Manual

THE ELECTRONIC CONTROLLER

Briefly described on page 6, the Electronic Controller is the
primary device used to move ETX model telescopes. Electronic
Controller functions include:
• Slewing the telescope (see Observing with the Electronic
Controller, page 6)
• Turning on the telescope motor drive to automatically track
celestial objects (when the telescope is polar aligned)
• Changing the hemisphere of operation, when required
• Changing tracking speed (see APPENDIX A, page 22)

Modes of Operation

The Electronic Controller can be set to operate in either of two
primary modes: the Alt/Az mode (used when the telescope is
operated in the altazimuth configuration; see page 9) and the
polar mode (used when the telescope is polar-aligned; see page
10).
• Alt/Az (altitude-azimuth, or vertical-horizontal) mode should
be chosen for all terrestrial operations of the telescope. In the
Alt/Az mode you can use the arrow keys
telescope to terrestrial or astronomical objects and, once you
locate them, you can follow these objects if they move.
However, in this mode astronomical tracking is not automatic
and requires continuous key pushes. The Electronic
Controller is factory pre-set to the Alt/Az mode.
• Polar mode should be chosen in cases where the telescope
is equipped with either the optional #880 (ETX–90EC) or #881
(ETX-125EC) Table Tripod, or #883 Deluxe Field Tripod,
permitting polar alignment of the telescope for extensive
astronomical observations. In this mode you can use the
arrow keys to slew the telescope to objects, as in the Alt/Az
mode above. In addition, the telescope's internal motor drive
is turned on, enabling fully automatic tracking of celestial
objects.
The following two methods are available to change the
Electronic Controller between the Alt/Az and polar modes:
1. Physically remove one of the mode screws (see Using the
Mode Screws, below).
2. Use the MODE key on the Electronic Controller, as described
in Electronic Controller Modes, opposite.

Using the Mode Screws

You can remove the two screws on the bottom rear of the
Electronic Controller handbox to change the default mode of the
Electronic Controller to Alt/Az or polar and, if polar, to the
hemisphere in which you are located.
NOTE:Mode screws A and B are the outer screws in the recess
directly under the letters A and B on the rear of the Electronic
Controller. Do not remove either of the inner two screws in the
recess.
1
Fig.12: Mode screws on rear of Electronic Controller.
(1) Mode .screw A; (2) Mode screw B.
Mode Screw A (1, Fig. 12): Remove mode screw A to make the
Northern hemisphere polar mode the automatic default of the
z
TELESCOPE FUNDAMENTALS
Electronic Controller when power is applied (i.e., the motor drive
is activated for operation in the Earth's Northern Hemisphere —
the U.S.A., Europe, Japan, etc.).
Mode Screw B (2, Fig. 12): Remove mode screw B to to make
the Southern Hemisphere polar mode the automatic default of
the Electronic Controller when power is applied (i.e., the motor
drive is activated for operation in the Earth's Southern
Hemisphere — Australia, South America, Africa, etc.).
NOTES:(1) Leaving both A and B screws in place (or removing
both screws) keeps the telescope in its original Alt/Az mode.
(2) Removing either A or B screw affects only the telescope's
default mode; you may still make mode changes at will during
telescope operation using the MODE key (see E l e c t ro n i c
Controller Modes, below).

Electronic Controller Modes

The Electronic Controller is in the Alt/Az mode when activated,
unless a mode screw has been removed. To use the Electronic
Controller to change to Northern or Southern Hemisphere polar
mode, or to use Alt/Az mode with one of the mode screws
to slew the
removed, use the following procedure:
1.
2.
2
Complete the Polar Alignment Procedure on page 12.
Complete steps 2 through 8 in O b s e rving with the
Electronic Controller (page 7) to initialize the Electronic
Controller.
3. Press and hold the MODE key (5, Fig. 6) until lights
1 and 2 are on steady and lights 3 and 4 start
blinking.
4. Press the SPEED key (3, Fig. 6) once. This changes
the system to polar mode for the Earth's Southern
Hemisphere, with the motor drive set to operate at
the sidereal rate.
5. Press the SPEED key a second time. This changes
the system to polar mode for the Earth's Northern
hemisphere, with the motor drive set to operate at
the sidereal rate.
6. Press the SPEEDkey a third time and the system
returns to the Alt/Az mode. In the Alt/Az mode the
motor drive does not activate when exiting from the
Mode function.
7. Use the SPEED key as described in the above
steps to cycle among these three modes (Alt/Az,
Southern Hemisphere polar, or Northern Hemi-
sphere polar) until the desired mode is shown by the
appropriate light configuration.
8. Press and hold the MODEkey until just one light is
on. This exits the Mode function. If you choose
Northern or Southern Hemisphere polar mode, the
motor drive starts operating at the sidereal rate.
9. Use the four arrow keys (1, Fig. 6) to slew the
telescope to the desired object. To change the slew
speed, press the SPEED key.
N OT E : See APPENDIX A (page 22) for adva n c e d
functions of the Electronic Controller.
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