Meade Instruments Corporation
Telescopes · Binoculars · Microscopes

ETX Astro Telescope and ETX Spotting Scope
 Instruction Manual
IMPORTANT NOTICE! Never use a telescope or spotting scope to look at the Sun! Observing the Sun, even for the shortest fraction of a second, will cause irreversible damage to your eye as well as physical damage to the telescope or spotting scope itself.
For high-magnification, high-resolution observation of terrestrial subjects, the Meade ETX Spotting Scope is one of the finest telescopes ever developed at any price. Explore the subtleties of a bird's feather structure from 50 yards; read license plates more than one mile in the distance; or use the ETX Spotting Scope for casual astronomical purposes. Applications of the ETX are almost limitless.

Note: "Spotting Scope" is a term used to define a telescope that is primarily intended for terrestrial (land) viewing, as opposed to astronomical applications. Notwithstanding this definition, the ETX Spotting Scope, as is discussed below, can also be used for casual astronomical observing. Similarly, the ETX Astro Telescope, by definition an astronomical telescope, is often used as a terrestrial instrument, as discussed in previous pages of this manual. Astronomical telescopes, including the ETX Astro, Telescope, normally include mounting systems and/or motor drives specifically designed for astronomical objecttracking. Thus the differences between a spotting scope and an astronomical telescope generally lie not in the optical design but in the mechanical design that makes it particularly suitable for its primary intended application.

Fig. 20: The ETX Spotting Scope
  1. Viewfinder Lens Cell
  2. Knurled Ring
  3. Viewfinder
  4. Front Alignment Screws
  5. Viewfinder Bracket
  6. Rear Alignment Screws
  7. 90° Eyepiece Holder
  8. Focus Know
  9. Knurled Ring of #932 45° Ericting Prism
  10. SP 26mm Eyepiece
  11. #932 45° Ericting Prism
  12. Flip-Mirror Control
  13. Tripod Adapter Block (1/4-20 thread)
  14. Photo Tripod (user-supplied)


[ toc ] 1. Parts Listing

When first opening the packing box of the ETX Spotting Scope, note carefully the following parts included with the telescope:

  • The ETX Spotting Scope optical tube assembly.
  • 8 x 21 mm Viewfinder, packed in a separate, small box.
  • Super PlössI (SP) 26mm eyepiece, packed in plastic storage container.
  • #932 45° Erecting Prism
  • Hex-wrench set with 2 (English-format) wrenches

The 8 x 21mm Viewfinder is packed separately from the main telescope in shipment to avoid the possibility of the viewfinder slipping in its bracket and scratching the viewfinder tube.

[ toc ] 2. Assembly Instructions

Assembly of the telescope requires only three quick steps: NOTE: The viewfinder should be chocked for correct focus prior to installation in the viewfinder bracket.

  1. Slide the viewfinder into its bracket (5, Fig. 20) with the rubber-eyecup-end of the viewfinder fitting first through the front end of the bracket. It may be necessary to slightly unthread the six alignment screws (4 and 6, Fig. 20) to fit the viewfinder into the bracket. With the viewfinder inside the bracket, tighten (to a firrn feel only) the six alignment screws down against the viewfinder tube. Alignment of the viewfinder is detailed on page 19.
  2. Remove the #932 45° Erecting Prism from its packing box. After unthreading the Photo Port cover (6, Fig. 1) thread the knurled ring (9, Fig. 20) of the #932 Prism on to the Photo Port. "Firm feel" tightening is sufficient. Note: The rear-cell thread of the ETX telescope is called the "Photo Port," since this port is also used for attachment of a 35mm camera body to the telescope
  3. Remove the SP 26mm eyepiece (10, Fig. 20) from its plastic storage container and place it in the eyepieceholder of the #932 Erecting Prism (11, Fig. 20) tightening the eyepiece-holder's thumbscrew to a firm feel.
Assembly of the ETX Spotting Scope is now complete.


[ toc ] 1. Quick Tips

  • Viewfinder Alignment with Main Telescope: When first attached to the telescope, the viewfinder and main optical tube are not aligned. Therefore, it is not possible to locate objects in the main telescope using the viewfinder. Procedures for aligning the viewfinder and main telescope are detailed on page 19 of this manual.
  • Flip-Mirror Orientation: Confirm that the Flip-Mirror Control (12, Fig. 20) is in the "down" position so light is directed to the eyepiece (see Telescope Controls, below).
  • Focus Knob: Sharp focusing of a telescopic image requires precise control of the focus knob (8, Fig. 20). Turn the focus knob slowly for clear viewing of 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 ] 2. Telescope Controls

Flip-Mirror Control (12, Fig. 20): The ETX includes an internal optically-flat mirror. The Flip-Mirror Control is "down" when the outer edge of the control is horizontal (parallel with the main tube of the telescope. It is in the "up" position when the control is vertical (perpendicular to the main telescope tube). The Flip-Mirror Control must be in the "down" position in order for light to reach the telescope's #932 Erecting Prism and eyepiece. Images seen through the prism will appear correctly oriented both up-and-down and left-to-right, just as they are normally seen without a telescope.

Alternately, placing the Flip-Mirror Control in the "up" position diverts incoming light to a right-angle and permits observations with the eyepiece in the 900 eyepiece-holder (7, Fig. 20). If the eyepiece is moved to this position, re-focusing is required, and, while the image is correctly oriented up-and-down, it appears reversed left-for-right. The 90° observing position is particularly advantageous when observing objects high in the sky, such as aircraft, or astronomical objects, such as the Moon.

Focus Knob (8, Fig. 20): Turning this knob causes a finelycontrolled internal motion of the telescope's primary mirror to achieve precise focus of the telescopic image. The ETX 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; rotate the focus knob counterclockwise to focus on near objects.

[ toc ] 3. Magnification

The magnification, or power, at which a telescope is operating is determined by two factors: the focal length of the telescope and the focal length of the eyepiece employed.

Telescope Focal Length: Generally speaking, telescope focal length is the distance that light travels inside the telescope before reaching a focus. In the mirror-lens design of the ETX, however, this focal length is, in effect, compressed by the telescope's secondary mirror, so that a long effective telescope focal length is housed in the short ETX optical tube. The ETX's focal length is 1250mm, or about 49". If the ETX were a classical refracting-type of telescope, its optical tube would thus be more than four feet long instead of the ETX's compact 11" tube length.

Eyepiece Focal Length: The eyepiece focal length is the distance light travels inside the eyepiece before reaching focus. Focal length is usually printed on the side of the eyepiece. The Meade ETX is supplied with one eyepiece as standard equipment, a Super Plössl (SP) 26mm eyepiece. Thus, the focal length of the provided eyepiece is 26mm. "Super Plössl" refers to the optical design of the eyepiece, a design specifically intended for high-performance telescopes and one which yields a wide, comfortable field of view with extremely high image resolution.

Technical note to the advanced amateur astronomer: The SP 26mm eyepiece supplied with Meade ETX telescopes is a special low-profile version of the standard Meade SP 26mm eyepiece and is about 114" (6mm) shorter than the standard eyepiece. This low-profile SP 26mm is designed to harmonize with the ultracompact scale of the ETX telescope and utilizes the exact same optics as the standard SP 26mm eyepiece. The SP 26mm low-profile eyepiece is not parfocal, however, with other eyepieces in the SP series (i.e., the eyepiece requires refocusing when it is interchanged with other SP eyepieces). Calculating Magnification: On a given telescope, such as the ETX, different eyepiece focal lengths are used to achieve different magnifications, from low to high. The standardequipment SP 26mm eyepiece, as stated above, yields 48X. Optional eyepieces (see page 20) and the #126 2X Barlow Lens are available for powers from 31X to over 300X. To calculate the magnification obtained with a given eyepiece, use this formula:

Power = Telescope Focal Length
Eyepiece Focal Length

Example: The power obtained with the ETX with the SP 26mm eyepiece is:

Power = 1250mm = 48X

The most common mistake of the beginning observer is to "overpower" the telescope by using high magnifications which the telescope's aperture and typical atmospheric conditions can not reasonably support. Keep in mind that a smaller, but bright and well-resolved, image is far superior to a larger, but dim and poorly resolved, one. Powers above about 30OX should be employed with the ETX only under the steadiest atmospheric conditions.

Most observers will want to have 2 or 3 eyepieces to achieve the full range of reasonable magnifications possible with the ETX Spotting Scope.

The ETX Spotting Scope utilizes the exact same astronomicalgrade optical system as its sister instrument, the ETX Astro Telescope. As such, the ETX Spotting Scope may theoretically be used for astronomical observations at powers up to about 30OX, or slightly higher. However, such high magnifications with the ETX Spotting Scope are impractical because the telescope does not include either the fork mounting system capable of polar alignment (see Polar Alignment, page 8) or the automatic-tracking motor drive of the ETX Astro Telescope (see The Motor Drive, page 10). Astronomical objects located at high power with the ETX Spotting Scope mounted on a photo tripod are also difficult to track due to the same limitations.

At more moderate powers, however, such as between 31 X and 63X, the ETX Spotting Scope can be used for observing the Moon and planets, as well as some objects in deep-space. Keep in mind that, notwithstanding the difficulty of tracking an astronomical object with the ETX Spotting Scope, the optical resolution of the image is identical to that of the ETX Astro Telescope, since both instruments use identical optical systems


The ETX Spotting Scope should be firmly attached to a suitable photo-tripod, using the 1/4-20 tripod adapter block (13, Fig. 20) located on the underside of the telescope's tube assembly. Unthread the metal dust cap from the front lens. The ETX Spotting Scope may now be used for observations, but be sure to read at least the remainder of this section before attempting to use the telescope. Keep in mind that the viewfinder has not yet been aligned to the main telescope. As a result, the observer must sight along the side of the main tube to locate objects. With the standard-equipment SP 26mm eyepiece mounted in the #932 450 Erecting Prism, as described above, the telescope yields 48-power, written "48X." Note: The dust cap should be replaced after each observing session.

Important Note: In the most discriminating applications, such as in observing delicate bird feather-stnicture at long distance, the ETXs intemal, optically-flat mirror yields a higher-resolution image than is possible with any prism, including the #932 45, Erecting Prism. In these special cases ETX users are advised to observe with the eyepiece in the 900 eyepiece-holder (17, Fig. 20) with the Flip-Mirror Control in the "up" position. This admonition applies only to situations requiring extraordinarily high optical resolution and where the observer's eye is welltrained to observe very fine detail. In typical applications of the telescope terrestrially no image differences between the two eyepiece locations will generally be noted.

[ toc ] 1. The Viewfinder

The ETX Spotting Scope 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 enable the easy centering of objects in the main telescope's field. Standard equipment with the ETX Spotting Scope is a viewfinder of 8-power and 21mm aperture, called an "8 x 21 mm viewfinder." Never use the Meade ETX Spotting Scope to look at the Sun! Observing the Sun, even for the shortest fraction of a second, will cause irreversible damage to your eye as well as physical damage to the telescope itself.

The ETX viewfinder, unlike most telescope viewfinders, presents a correctly oriented image, both up-and-down and left-to-right. This orientation particularly facilitates the location of terrestrial objects. The 8 x 21mm viewfinder is also a tremendous aid in locating faint astronomical objects before their observation in the main telescope.

[ toc ] a. Focusing the Viewfinder

The ETX viewfinder has been factory pre-focused to objects located at infinity. Individual eye variations, however, may require that the viewfinder be re-focused for your eye. Prior to installing the viewfinder in the viewfinder bracket (5, Fig. 2), check the focus by looking through the viewfinder. Point the viewfinder at a distant object; if the viewfinder image is not sufficiently in focus for your eye, it may be re-focused as follows:

  1. Loosen the knurled lock-ring (2, Fig. 20 located near the viewfinder's objective (front) lens (1, Fig. 20). Unthread this ring (counterclockwise, as seen from the eyepiece- end of the viewfinder) by several full turns.
  2. Focus the viewfinder by rotating the objective lens cell (1, Fig. 20) 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.
  3. 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.
  4. Place the viewfinder into the viewfinder bracket (5, Fig. 20) on the main telescope. Gently tighten the six alignment screws (4 and 6, Fig. 20), then proceed with alignment of the viewfinder.

[ toc ] b. Alignment of 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 place. To align the viewfinder follow this procedure:

  1. The viewfinder bracket (5, Fig. 20) includes six alignment screws (4 and 6, Fig. 20). Turn the 3 rear-most alignment screws (6, Fig. 20) 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 of the two other 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 main telescope's field and engage the R.A. Lock and Dec Lock so that the object can not move in the field.
  3. While looking through the viewfinder, turn one or more of the 3 front-most viewfinder alignment screws (4, Fig. 20), until the crosshairs of the viewfinder point at precisely the same position as the main telescope. 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, the viewfinder will remain aligned indefinitely.

[ toc ] c. Using the Viewfinder

To locate any object, terrestrial or astronomical, first center the object in the crosshairs of the viewfinder; the object will then also be centered in the field of the main telescope. Note: If you intend to use higher observing magnifications, first locate, center, and focus the object using a low-power eyepiece (e.g., the SP 26mm eyepiece). Objects are easier to locate and center at low powers; higher power eyepieces may then be employed simply by changing eyepieces.

[ toc ] 2. Terrestrial Observing

Viewing terrestrial objects require observers to look along the earth's surface through heat waves. These heat waves often cause degradation of image quality. Low power eyepieces, like the SP 26mm eyepiece provided with the ETX Astro Telescope, magnify these heat waves less than higher powered eyepieces. Therefore, low power eyepieces provide a steadier, higher quality image. If the land image is fuzzy or ill- defined, drop down to a lower power, where the earth's heat waves will not have such a deleterious effect on image quality. Observing in early morning hours, before the earth has built up internal heat, is generally more advantageous than during late- afternoon hours.

[ toc ] 3. Photography with the ETX Spotting Scope

Photography through the ETX Spotting Scope requires the addition of the optional #64 T-Adapter (Fig. 21). With the #64 T-Adapter attached to the telescope, through-the-telescope photography is possible with any 35mm camera body with removable lens. In this way the telescope effectively becomes the lens of the camera.

Fig. 21: Using the #64 T-Aclapter with the ETX Spotting Scope. (1) Flip-Mirror Control in "down" position; (2) T-Mount; (3) Short section of #64 T-Adapter; (4) Knurled ring.
For through-the-telescope photography, turn the Flip-Mirror Control (1, Fig. 21) to the "down" position (see Telescope Controls, page 18), allowing light to pass straight-th rough the telescope and out the Photo Port (6, Fig. 1). With the Flip-Mirror Control in the "down" position and the Photo Port's dust cover removed, the front lens of the telescope can be seen when looking through the Photo Port. The #64 T-Adapter threads on to the Photo Port, followed by a T-Mount for the particular brand of 35mm camera being used, followed in turn by the camera body itself (with camera lens removed).

Note that the #64 T-Adapter consists of two sections (1 and 2, Fig. 11) which are threaded together in shipment. Either of the following photographic mounting formats may be used to couple the camera body to the telescope's Photo Port thread.

Format 1: Camera Body + T-Mount + Section (1) of the #64 T-Adapter. Format 1 utilizes the short section only of the #64 T-Adapter (3, Fig 21) to permit close-coupling of a camera body to the telescope at an effective photographic speed of f/14 and a transmission value (the so-called "T"-value) of 18. In this format vignetting will occur: the photographic image will appear on film as a circle, without illuminating the complete 35mm frame.

Format 2: Camera Body + T-Mount + Sections (1) and (2) of the #64 T-Adapter. Format 2 utilizes both sections of the #64 T-Adapter threaded together to form a rigid unit as shown in Fig. 11, the telescope is operating at a photographic speed of f/16 and T-value of 23, but without any field vignetting: images are illuminated to the edges of a standard 35mm frame.

To frame an object in the viewfinder of the 35mm camera body, loosen slightly the knurled ring (4, Fig. 21) which threads the #64 T-Adapter to the telescope's Photo Port; rotate the camera body to achieve proper framing of the object; then re-tighten the knurled ring.

Photography through a long lens such as the ETX requires special technique for good results, and the photographer should probably expect to waste a roll or two of film in acquiring this technique. Long-lens photography has its own rewards, however; rewards that short-focus lenses can not duplicate.

A few tips on photography through the ETX:

  1. Use a rigid, heavy-duty photo tripod as a platform for the telescope. At effective focal lengths of 1250mm to 1450mm, even small external vibrations can easily ruin an otherwise good photo.
  2. Use a cable-operated shutter release. Touching the camera body to initiate shutter operation will almost certainly introduce undesirable vibrations.
  3. Focus the image with extreme care. While observing the subject through the camera's reflex viewfinder, turn the ETX's focus knob (8, Fig. 20) to achieve the sharpest possible focus.
  4. Correct shutter speeds vary widely, depending on lighting conditions and the film used. Trial-and-error is the best way to determine the proper shutter speed in any given application.
  5. Terrestrial photography through the ETX is sensitive to heat waves rising from the earth's surface. Long distance photography is best accomplished in the early morning hours, before the earth has had time to build up heat.

Note: Astronomical photography is not practical through the ETX Spotting Scope, since the telescope is not mounted on a motor driven astronomical (equatorial) mount Photos of the Moon or planets taken with the ETX Spotting Scope mounted on a photo tripod will appear blurred due to the earth's rotation during the period of the exposure.


[ toc ] 1. General Maintenance

The ETX Telescope is a precision optical instrument designed to yield a lifetime of rewarding applications. Given the care and respect due any precision instrument, the ETX will rarely, if ever, require factory servicing or maintenance. Maintenance guidelines include:

  1. Avoid cleaning the telescope's optics: a little dust on the front surface of the telescope's correcting lens causes virtually no degradation of image quality and should not be considered reason to clean the lens.
  2. When absolutely necessary, dust on the front lens should be removed with very gentle strokes of a camel hair brush or blown off with an ear syringe (available at any pharmacy).
  3. Organic materials (e.g., fingerprints) on the front lens may be removed with a solution of 3 parts distilled water to 1 part isopropyl alcohol. You may also add 1 drop of biodegradable dishwashing soap per pint of solution. Use soft, white facial tissues and make short, gentle strokes. Change tissues often.

    CAUTION: Do not use scented or lotioned tissues or damage could result to the optics.

  4. In the very rare situation where cleaning the inside surface of the corrector lens becomes necessary, unthread the lens cell located at the front of the main tube. The entire correcting lens and secondary mirror system is mounted in this cell. The lens cleaner solution described in step c may be used to clean the inside surface of the lens. DO NOT use a commercial photographic lens cleaner.

    CAUTION: Do not touch the aluminized circular surface of the secondary mirror with your finger, a tissue, or any other object. Scratching of the mirror surface will otherwise almost certainly result.

    Note: When cleaning the inside surface of the correcting lens, leave the lens mounted in its metal cell throughout the process. Do not remove the lens from its metal housing or else optical alignment of the lens will be lost, necessitating a return of the telescope to the Meade factory.

  5. If the ETX is used outdoors on a humid night, water condensation on the telescope surfaces will probably result. While such condensation does not normally cause any damage to the telescope, it is recommended that the entire telescope be wiped down with a dry cloth before the telescope is packed away. Do not, however, wipe any of the optical surfaces. Rather, simply allow the telescope to sit for some time in the warm indoor air, so that the wet optical surfaces can dry unattended.
  6. The super-gloss anodized finish of the ETX's deep-violet optical tube will fade if left in direct sunlight for prolonged periods.
  7. Do not leave the ETX telescope inside a sealed car on a warm summer day; excessive ambient temperatures can damage the telescope's internal lubrication and electronic circuitry.
  8. Two (English-format) hex wrenches are provided with each ETX Spotting Scope. These wrenches are used as follows:
    • Small wrench (.050"): Use the small wrench to tighten the set-screws of any knobs which may loosen (e.g., Focus knob, or Flip-Mirror Control knob).
    • Medium wrench (1/16"): This wrench is used to detach the viewfinder bracket from the telescope's rear- cell.

[ toc ] 2. Storage and Transport

When not in use, store the telescope in a cool, dry place. Do not expose the instrument to excessive heat or moisture. It is best to store the telescope in its original box. If shipping the telescope, use the original box and packing material to protect the telescope during shipment.

When transporting the telescope, take care not to bump or drop the instrument; this type of abuse can damage the optical tube and/or the front correcting lens.

[ toc ] 3. Inspecting the Optics

A Note about the "Flashlight" Test: If a flashlight or other high-intensity light source is pointed down the main telescope tube, the view (depending upon the observer's line of sight and the angle of the light) may reveal what appears to be scratches, dark or bright spots, or just generally uneven coatings, giving the appearance of poor quality optics. These effects are only seen when a high intensity light is transmitted through lenses or reflected off the mirrors, and can be seen on any high quality optical system, including giant research telescopes.

The optical quality of a telescope cannot be judged by the "flashlight" test; the true test of optical quality can only be conducted through careful star testing.

[ toc ] 4. Troubleshooting

The following suggestions may be helpful if you are having difficulty observing through the ETX Spotting Scope:

  1. Confirm that all the lens or mirror covers have been removed from the telescope.

    Never use the ETX telescope to look at the Sun! Observing the Sun, even for the shortest fraction of a second, will cause instant and irreversible damage to the eye, as well as physical damage to the telescope Itself.

  2. Confirm that the Flip-Mirror Control (12, Fig. 20) is in the "down" position if using the #932 Erecting Prism (11, Fig. 20) or doing photography with the ETX. Confirm that the Flip-Mirror Control is in the "up" position if using the Eyepiece Holder (7, Fig. 20) so light is directed to the eyepiece (10, Fig. 20) (see Telescope Controls, page 18).
  3. When objects appear in the viewfinder but not in the telescope, the viewfinder is not properly aligned with the telescope. Before the ETX is used the first time, the viewfinder must be aligned to the main telescope (see The Viewfinder, page 19). Once aligned, locate objects in the viewfinder first, then move to the main telescope.
  4. Air conditions inside a warm house or building may distort terrestrial or celestial images and make it difficult, if not impossible, to obtain a sharp focus. For optimal viewing, use the telescope outside in the open air instead of observing through an open or closed window or screen.
  5. For clear viewing of objects, turn the focus knob (8, Fig. 20) slowly since the "in-focus" point of a telescope is precise.
  6. The optics within your telescope need time to adjust to the outside ambient temperature to provide the sharpest image. To "cool down" the optics, set your telescope outside for 10 to 15 minutes before you begin observing.

[ toc ] 5. Meade Customer Service

If you have a question concerning your ETX telescope, call Meade Instruments Customer Service Department at (949) 451-1450, or fax at (949) 451-1460. Customer Service hours are 8:30AM to 4:30PM, Pacific Time, Monday through Friday. In the unlikely event that your ETX requires factory servicing or repairs, write or call the Meade Customer Service Department first, before returning the telescope to the factory, giving full particulars as to the nature of the problem, as well as your name, address, and daytime telephone number. The great majority of servicing issues can be resolved by telephone, avoiding return of the telescope to the factory.

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