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Meade ETX-90EC Astro Telescope Instruction Manual
WARNING! Never use the Meade ETX-90EC Astro Telescope to look at the Sun! Looking at or near the Sun will cause instant and irreversible damage to your eye. Eye damage is often painless, so there is no warning to the observer that damage has occurred until it is too late. Do not point the telescope or its viewfinder at or near the Sun. Do not look through the telescope or its viewfinder as it is moving. Children should always have adult supervision while observing.

The Meade ETX-90EC Astro Telescope is an extremely versatile, high-resolution imaging system that, with advanced features similar to larger and more specialized telescopes, can be used by casual observers and serious astronomers alike. With pushbutton controls, automatic tracking of celestial objects (with one of the optional tripods), and diffraction-limited imaging, the ETX-90EC may be all the telescope ever required by many terrestrial and astronomical observers.

As a first telescope the ETX-90EC reveals nature in an ever-expanding level of detail: observe the feather structure of a bird from 50 yards or study the rings of the planet Saturn from a distance of 800 million miles. Beyond the Solar System observe nebulae, star clusters, galaxies, and other deep-sky objects. The Meade ETX-90EC is an instrument fully capable of growing with the user's interest.

As a second telescope for the amateur astronomer who may already own a larger instrument the ETX-90EC represents extreme portability without sacrificing the most demanding requirements for optical quality and field performance.

The Meade ETX-90EC is one of the most revolutionary telescope systems ever developed. ETX-90EC users should read this manual thoroughly, so that full advantage can be taken of all the advanced features of this amazing instrument.

[ toc ] The Electronic Controller

Fig.2: Electronic Controller.
Control of the ETX-90EC is through pushbutton operation of the standard-equipment Electronic Controller (Fig. 2). Nearly all functions of the telescope are accomplished through the Electronic Controller with just a few button pushes:

  • Move the telescope in two axes (up-and-down or left-to-right) at any of four drive speeds for precise tracking of astronomical or terrestrial objects.
  • Use the optional #880 Table Tripod or #883 Deluxe Field Tripod to mount the telescope in the "polar" mode for fully automatic tracking of celestial objects with the telescope's motor drive (see OPTIONAL ACCESSORIES).
  • When in the polar mode, switch the motor drive between northern and southern hemisphere operation for observing from anywhere in the world.

A detailed description of the functions and operation of the Electronic Controller is found in Electronic Controller Functions.

[ toc ] Parts Listing

In keeping with the ETX philosophy of elegant simplicity, the ETX-90EC is virtually completely assembled at the Meade factory; getting the telescope ready for first observations requires only a few minutes. When first opening the packing box, note carefully the following parts:

  • The ETX-90EC Astro Telescope with fork mount system.
  • Electronic Controller with attached coil cord.
  • 8 x 21mm viewfinder, packed in a separate, small box.
  • Super Plössl (SP) 26mm eyepiece, packed in a plastic storage container, in a separate small box.
  • Hex-wrench set (2 wrenches), packed with the manual.

The viewfinder is packed separately from the main telescope to avoid the possibility of the viewfinder slipping in its bracket and scratching the viewfinder tube during shipment.

[ toc ] Assembly Instructions

Assembly of the ETX-90EC requires eight AA-size (user-supplied) batteries and only four steps:

NOTE: Prior to installing the viewfinder verify that it is properly focused. Look at a distant object and see if the view is sharp. If it is, proceed with these assembly instructions. If it is not, see Focusing the Viewfinder.

Fig. 3: Bottom view of ETX-90EC showing eight AA-size batteries mounted inside the battery compartment. (1) High-Latitude Tripod Leg Hole; (2) Drive Base; (3) Alternate Tripod Leg Hole; (4) Battery Compartment Cover; (5) Battery Compartment; (6) Release Latches.
  1. Slide the eyepiece end of the viewfinder through the front of the viewfinder bracket (20, Fig. 1). It may be necessary to slightly unthread the six alignment screws (19, Fig. 1) to fit the viewfinder into the bracket. Once the viewfinder is in place, tighten (to a firm feel only) the six alignment screws against the viewfinder tube. To align the viewfinder, see Aligning the Viewfinder.
  2. Remove the SP 26mm eyepiece (1, Fig. 1) from its container and place it in the eyepiece holder (4, Fig. 1). Tighten the thumbscrew (3, Fig. 1) to a firm feel only.
  3. The telescope's battery compartment (6, Fig. 3) is located at the bottom of the drive base. Place the telescope securely on its side as shown in Fig. 3. Open the battery compartment by simultaneously depressing the two release latches (4, Fig. 3) and pulling the battery cover (5, Fig. 3) away from the drive base. Insert eight AA-size batteries into the battery compartment, oriented as shown on the battery mounting board. Replace the cover.
  4. Place the telescope in an upright position on a flat surface. Be certain that the power switch on the computer control panel (1, Fig. 4) is in the OFF position. Plug the coil cord for the Electronic Controller into the HBX port (3, Fig. 4). Basic assembly of the ETX-90EC is now complete.


[ toc ] Quick Tips

  • Rotational Limits: The telescope base and fork mount are designed with internal "rotational limit stops." The horizontal limit stop prevents the telescope from rotating more than 630° to avoid damage to the internal wiring. The vertical limit stop prevents the viewfinder from contacting the fork mount when the telescope is pointed upward just past 90° and prevents the optical tube from contacting the base if pointed downward more than 30°. Do not force the telescope to move beyond these stops or damage to the telescope will result.
  • Vertical Lock; Declination Setting Circle: The vertical lock knob (6, Fig. 1) is a knurled knob located on the fork arm to the right of the focus knob (9, Fig. 1). Mounted beneath the knob is a circular scale with no numbers. Do not confuse this scale with the Dec setting circle (18, Fig. 1) on the opposite fork arm which has a number scale used to locate astronomical objects.
  • A Note on Indoor Viewing: While casual, low-power observations may be made with the telescope through an open or closed window, the best observing is always done outdoors. Temperature differences between inside and outside air and/or the low quality of most home window glass can cause blurred images through the telescope. Do not expect high-resolution imaging under these conditions.

[ toc ] Telescope Controls

An important array of features and manual controls facilitates operation of the ETX-90EC. Be sure to become acquainted with all of these controls before attempting observations through the telescope.

Horizontal Lock (10, Fig. 1): Controls manual horizontal rotation of the telescope while sitting upright as shown in Fig. 1. Turning the horizontal lock counterclockwise unlocks the telescope, enabling it to be freely rotated by hand about the horizontal axis. Turning the horizontal lock clockwise prevents the telescope from being rotated manually, but engages the horizontal motor drive clutch for Electronic Controller operation. When polar aligned, the horizontal lock serves as the Right Ascension, or R.A. lock (see Right Ascension).

Vertical Lock (6, Fig. 1): Controls manual vertical movement of the telescope while sitting upright as shown in Fig. 1. Turning the vertical lock counterclockwise unlocks the telescope enabling it to be freely rotated by hand about the vertical axis. Turning the vertical lock clockwise (to a firm feel only) prevents the telescope from being moved manually, but engages the vertical motor drive clutch for Electronic Controller operation. When polar aligned, the vertical lock serves as the Declination, or Dec lock (see Declination).

Focus Knob (9, Fig. 1): Causes a finely-controlled internal motion of the telescope's primary mirror to achieve precise image focus. The ETX-90EC can be focused on objects from a distance of about 11.5 ft (3.5m) to infinity. Rotate the focus knob clockwise to focus on distant objects; counterclockwise to focus on near objects.

Flip-Mirror Control (16, Fig. 1): The ETX-90EC includes an internal optically-flat mirror. With the flip-mirror control in the "up" position, as shown in Fig. 1, light is diverted at a 90° angle to the eyepiece. Alternately, with the flip-mirror control in the "down" position, light proceeds straight through the telescope and out the photo port (17, Fig. 1) for telephoto or astronomical photography using the optional #64 T-Adapter, or for observing with the optional #932 45° Erecting Prism (see OPTIONAL ACCESSORIES).

NOTE: The flip-mirror control is in the "up" position when the control is vertical (perpendicular to the telescope tube). It is "down" when the control is horizontal (parallel with the telescope tube).

[ toc ] Computer Control Panel

Fig. 4: Computer Control Panel. (1) ON/OFF Switch; (2) Auxiliary Ports; (3) Handbox Port; (4) 12v Connector; (5) Power Indicator Light.
The ETX-90EC computer control panel (Fig. 4) includes a connector for either the standard-equipment Electronic Controller or the optional #497 ETX Autostar Computer Controller; an external power supply connector; and two auxiliary ports for the addition of ETX-90EC accessories (see OPTIONAL ACCESSORIES).

ON/OFF (1, Fig. 4): When the ON/OFF switch is moved to the ON position, the red power indicator light (5, Fig. 4) illuminates and power is supplied to the Electronic Controller and to the telescope's motor drive.

AUX (2, Fig. 4): Two identical auxiliary ports provide connections for current and future Meade accessories.

CAUTION: Using products other than standard Meade accessories may cause damage to the telescope's internal electronics and may void the Meade warranty.
HBX (3, Fig. 4): The HBX (handbox) port is designed to accept the plug from the coil cord of the Electronic Controller or the optional #497 ETX Autostar Computer Controller.

12v (4, Fig. 4): The 12v connector is designed to accept an external power supply such as the optional #541 AC adapter or the #607 DC automobile cigarette lighter adapter (see OPTIONAL ACCESSORIES). When one of these alternate powering options is used, the internal batteries are disconnected from the power circuit.

NOTE: Always remove the batteries if they are not to be used for a long period of time.

[ toc ] Electronic Controller Functions

Fig. 5: Electronic Controller. (1) Arrow Keys; (2) Indicator Lights; (3) SPEED Key; (4) Coil Cord; (5) MODE Key; (6) OUT Key; (7) IN Key.
The Electronic Controller provides the observer with the means to control the telescope motors from a compact handbox. The Electronic Controller (Fig. 5) has soft-touch keys designed to have a positive feel, even through gloves.

Primary functions of the Electronic Controller are to move (slew) the telescope, indicate the slew speed, and to operate the optional #1244 Electric Focuser (see OPTIONAL ACCESSORIES). Other functions are also possible when using the MODE key (see Electronic Controller Modes, and APPENDIX A).

Arrow Keys (1, Fig. 5): The four arrow keys move (slew) the telescope in four directions (i.e., up-and-down or left-to-right) at any one of four different slew speeds (see SPEED Key).

Important Note: While using the arrow keys to slew to an object, when reversing direction there may be a slight pause in the slew as the telescope motors compensate for the reversal of the internal gears.

Indicator Lights (2, Fig. 5): Four red LED (Light Emitting Diode) lights are used to indicate the current slew speed. NOTE: For purposes of this manual, the lights are identified as 1 through 4, with 1 being the top light and 4 the bottom light.

Indicator Light Key
The procedures in this manual identify the status of the four indicator lights in a box to the left of the appropriate step. They are depicted as On, Blinking or Off, depending on the mode at that point.

SPEED Key (3, Fig. 5): The SPEED key is used to change the speed at which the telescope slews when the arrow keys are pressed. Each press of the SPEED key changes the slew speed to the next slower setting. If already on the slowest slew speed (Light 4), pressing the SPEED key cycles back to the highest speed (Light 1). Slew speeds are signified by the indicator lights (2, Fig. 5).

MODE Key (5, Fig. 5): Pressing and holding the MODE key puts the Electronic Controller into the Mode function (see Electronic Controller Modes).

OUT Key (6, Fig. 5): The OUT key is used in conjunction with the optional #1244 Electric Focuser (see OPTIONAL ACCESSORIES) to move the focus point outward.

IN Key (7, Fig. 5): The IN key is used in conjunction with the optional #1244 Electric Focuser to move the focus point inward.

[ toc ] First Observations

Unthread the metal dust cap from the front lens of the telescope (counterclockwise), and the ETX-90EC may now be used for terrestrial (land) observing.

NOTE: The dust cap should be replaced after each observing session and the power turned off to the telescope. Verify that any dew that might have collected during the observing session has evaporated prior to replacing the dust cap. With the SP 26mm eyepiece inserted in the telescope's eyepiece holder, the telescope is operating at 48-power (see Understanding Magnification).

Objects viewed through the eyepiece are correctly oriented up-and-down in the telescope but are reversed left-for-right. Image orientation is discussed further in Terrestrial Observing. The flip-mirror control (16, Fig. 1) must be in the "up" position in order to observe an image through the telescope's eyepiece (see Flip-Mirror Control).

For the ultimate viewing experience it is important to become familiar with the features of the ETX-90EC and the functions of the Electronic Controller, below. Upon completing this chapter make first observations of a simple land object several hundred yards in the distance - perhaps a telephone pole or a building. Locate objects first in the viewfinder before viewing them in the main telescope (see Aligning the Viewfinder). Practice focusing on the object using the focus knob (9, Fig. 1) and centering the object in the eyepiece using the Electronic Controller arrows keys (1, Fig. 5).

[ toc ] Observing with the Electronic Controller

With the Electronic Controller in the factory pre-set "Alt/Az" (vertical-horizontal) mode, the Electronic Controller arrow keys permit pushbutton movements (slewing) of the telescope. To move the telescope using the Electronic Controller:

  1. Set the telescope on a level and stable surface, or mount to the Meade #883 Deluxe Field Tripod (see OPTIONAL ACCESSORIES).
  2. Insert a low-power eyepiece (e.g., SP 26mm) into the eyepiece holder (4, Fig. 1) and tighten the eyepiece thumbscrew (3, Fig. 1).
  3. Tighten the vertical and horizontal locks (6 and 10, Fig. 1).
  4. Verify that the power switch (1, Fig. 4) on the telescope's computer control panel is OFF.
  5. Attach the Electronic Controller coil cord (4, Fig. 5) to the HBX port (3, Fig. 4) on the computer control panel.
  6. Flip the power switch to ON. The power indicator light (5, Fig. 4) on the computer control panel comes on and all four Electronic Controller indicator lights (2, Fig. 5) blink rapidly.
  7. Press any key on the Electronic Controller and the telescope slews momentarily in the vertical and horizontal directions to test the motors.
  8. When the test is complete, Light 1 comes on steady; Lights 2, 3, and 4 turn off.
  9. Use the four arrow keys (1, Fig. 5) to slew the telescope to the desired object. To change the slew speed, press the SPEED key.
  10. Fine-adjust the position of the object with the Electronic Controller arrow keys so that it is centered in the viewfinder. The object is now ready to be viewed through the telescope's eyepiece.

Observing Tip: If the Electronic Controller has previously been placed in the polar mode (see Electronic Controller Modes) and Alt/Az operation is desired, flip the telescope power switch to OFF and perform steps 6, 7, and 8 above. The telescope is now in the Alt/Az mode. This procedure does not work if one of the mode screws has been removed (see Using the Mode Screws).


Fig. 6: The Viewfinder. (1) Front Lens Cell; (2) Knurled Lock-Ring; (3) Viewfinder; (4) Front Alignment Screws; (5) Viewfinder Bracket; (6) Rear Alignment Screws; (7) Viewfinder Eyepiece.
The ETX-90EC, as with almost all astronomical telescopes, presents a fairly narrow field of view to the observer. As a result it is sometimes difficult to locate and center objects in the telescope's field of view. The viewfinder, by contrast, is a low-power, wide-field sighting scope with crosshairs that enables the easy centering of objects in the eyepiece of the main telescope's field of view. Standard-equipment with the ETX-90EC is a viewfinder with 8-power magnification and a 21mm aperture, called an "8 x 21mm viewfinder."

The ETX-90EC viewfinder, unlike most telescope viewfinders, presents a correctly oriented image, both up-and-down and left-to-right. This orientation makes it easy to locate objects. The 8 x 21mm viewfinder is also a tremendous aid in locating faint astronomical objects before their observation in the main telescope's eyepiece.

[ toc ] Focusing the Viewfinder

The ETX-90EC viewfinder is factory pre-focused to objects located at infinity. Individual eye variations, however, may require that the viewfinder be re-focused. Prior to installing the viewfinder in the viewfinder bracket (5, Fig. 6), check the focus by looking through the viewfinder. Point the viewfinder at a distant object; if the viewfinder image is not in sharp focus, it may be re-focused for your eye as follows:

  1. If the viewfinder has already been mounted in the viewfinder bracket (5, Fig. 6), remove it by slightly unthreading the six alignment screws (4 and 6, Fig. 6) until the viewfinder can slip easily out of the bracket.
  2. Loosen the knurled lock-ring (2, Fig. 6) located near the viewfinder's front lens cell (1, Fig. 6). Unthread this ring (counterclockwise, as seen from the eyepiece-end of the viewfinder) by several turns.
  3. Focus the viewfinder by rotating the front lens cell in one direction or the other, until distant objects observed through the viewfinder appear sharp. One or two rotations of the viewfinder lens have a significant effect on image focus.
  4. Once correct focus is reached, lock the focus in place by threading the knurled lock-ring snugly clockwise up against the viewfinder's lens cell.
  5. Place the viewfinder into the viewfinder bracket on the main telescope. Gently tighten the six alignment screws then proceed with Aligning the Viewfinder.

[ toc ] Aligning the Viewfinder

In order for the viewfinder to be useful, it must first be aligned with the main telescope, so that both the viewfinder and the main telescope are pointing at precisely the same location. To align the viewfinder follow this procedure:

Fig. 7: Aligning the Viewfinder.

  1. The viewfinder bracket (5, Fig. 6) includes six alignment screws (4 and 6, Fig. 6). Turn the three rear alignment screws (6, Fig. 6) so that the viewfinder tube is roughly centered within the viewfinder bracket, as viewed from the eyepiece-end of the telescope.

    NOTE: Do not overtighten the alignment screws. When tightening one screw it may be necessary to loosen one or both of the two other alignment screws.

  2. Using the SP 26mm eyepiece, point the main telescope at some easy-to-find, well-defined land object, such as the top of a telephone pole. Center the object precisely in the eyepiece's field of view, then tighten the vertical and horizontal locks (6 and 10, Fig. 1) so that the object does not move (1, Fig. 7).

  3. While looking through the viewfinder, turn one or more of the three front viewfinder alignment screws (4, Fig. 6), until the crosshairs of the viewfinder point at precisely the same position as the view through the eyepiece of the main telescope (2, Fig. 7).

Re-check that the viewfinder's crosshairs and the main telescope are now pointing at precisely the same object. The viewfinder is now aligned to the main telescope. Unless the alignment screws are disturbed or the viewfinder jarred, the viewfinder should remain aligned indefinitely.

[ toc ] Using the Viewfinder

To locate any object, terrestrial or astronomical, first center the object in the crosshairs of the viewfinder; the object should also then be centered in the field of view of the main telescope.

Observing Tip: If higher observing magnifications are intended, first locate, center, and focus the object using a low-power eyepiece (e.g., the SP 26mm eyepiece). Then remove the low power eyepiece and replace with a higher power eyepiece; the object should still be centered in the field of view. Objects are much easier to locate and center at lower powers; higher power may then be employed simply by changing eyepieces.

Chapter 2: Telescope Fundamentals

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