Meade ETX-90EC TELESCOPE FUNDAMENTALSz, The Electronic Controller, Modes of Operation

TELESCOPE FUNDAMENTALSz

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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 to slew the 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.

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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

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 Electronic 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 removed, use the following procedure:

1.Complete the Polar Alignment Procedure on page 12.

2.Complete steps 2 through 8 in Observing 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.

NOTE: See APPENDIX A (page 22) for advanced functions of the Electronic Controller .

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