Meade ETX-90EC User manual

Meade ETX
-
90EC Astro Telescope Instruction Manual
POLAR ALIGNMENT
For extensive astronomical observing the telescope is best mounted in the polar
configuration. In polar alignment the telescope is oriented so that the horizontal
and vertical axes of the telescope are lined up with the celestial coordinate
system (see Fig. 10).
To polar align the ETX-90EC it is essential to have an understanding of how and
where to locate celestial objects as they move across the sky. This section
provides a basic introduction to the terminology of polar-aligned astronomy, and
includes instructions for finding the celestial pole and for following objects in the
night sky using Declination and Right Ascension.
Fig. 12: Examples of AltAz and polar mounting of the ETX-
90EC to the optional #883 Deluxe Field Tripod.
Celestial Coordinates
Celestial objects are mapped according to a coordinate system on the Celestial Sphere (Fig. 13), an imaginary
sphere surrounding Earth on which all stars appear to be placed. This celestial object mapping system is
analogous to the Earth-based coordinate system of latitude and longitude.
The poles of the celestial coordinate system are defined as
those two points where the Earth's rotational axis, if extended
to infinity, north and south, intersect the celestial sphere. Thus,
the North Celestial Pole (1, Fig. 13) is that point in the sky
where an extension of the Earth's axis through the North Pole
intersects the celestial sphere. This point in the sky is located
near the North Star, Polaris.
In mapping the surface of the Earth, lines of longitude are
drawn between the North and South Poles. Similarly, lines of
latitude are drawn in an east-west direction, parallel to the
Earth's Equator. The Celestial Equator (2, Fig. 13) is a
projection of the Earth's Equator onto the celestial sphere.
Just as on the surface of the Earth, in mapping the celestial sphere, imaginary lines have been drawn to form a
coordinate grid. Thus, object positions on the Earth's surface are specified by their latitude and longitude. For
example, you could locate Los Angeles, California, by its latitude (+34°) and longitude (118°); similarly, you could
locate the constellation Ursa Major (which includes the Big Dipper) by its general position on the celestial sphere:
R.A.: 11hr; Dec: +50°.
•Right Ascension: The celestial analog to Earth longitude is called "Right Ascension," or "R.A.," and is
measured in time on the 24 hour "clock" and shown in hours ("hr"), minutes ("min") and seconds ("sec")
from an arbitrarily defined "zero" line of Right Ascension passing through the constellation Pegasus. Right
WARNING! Never use the
Meade ETX-90EC Astro
Telescope to look at the Sun!
Looking at or near the Sun
will
cause instant andirreversible 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.
Fig. 13: Celestial Sphere.

Ascension coordinates range from 0hr 0min 0sec to 23hr 59min 59sec. Thus there are 24 primary lines of
R.A., located at 15 degree intervals along the celestial equator. Objects located further and further east of
the prime Right Ascension grid line (0hr 0min 0sec) carry increasing R.A. coordinates.
•Declination: The celestial analog to Earth latitude is called Declination, "Dec", and is measured in
degrees, minutes and seconds (e.g., 15°27' 33"). Declination shown as north of the celestial equator is
indicated with a "+" sign in front of the measurement (e.g., the Declination of the North Celestial Pole is
+90°), with Declination south of the celestial equator indicated with a "-" sign (e.g., the Declination of the
South Celestial Pole is -90°). Any point on the celestial equator itself (which, for example, passes through
the constellations Orion, Virgo and Aquarius) is specified as having a Declination of zero, shown as 0°0'
0".
All celestial objects are specified in position by their celestial coordinates of Right Ascension and Declination.
Locating the Celestial Pole
To get basic bearings at an observing location, take note of where the sun rises (East) and sets (West) each day.
After the site is dark, face north by pointing your left shoulder toward where the sun set. To precisely point at the
pole, find the North Star (Polaris) by using the Big Dipper as a guide (Fig. 16).
Polar Alignment Procedure
As the Earth rotates once on its axis every 24 hours, astronomical objects appear to move across the sky in an arc.
This apparent motion (see Sidereal Rate) is not obvious to the unaided eye, but viewed through a serious
telescope such as the ETX-90EC, this motion is rapid indeed. If the motor drive has not been engaged, objects
centered in the telescope's eyepiece move entirely out of the field of view in 30 to 160 seconds, depending on the
magnification employed.
For easy tracking of astronomical objects the ETX-90EC should be polar aligned.
There are two mounting methods available to polar align the ETX-90EC: by use of the optional #883 Deluxe Field
Tripod or the #880 Table Tripod (see OPTIONAL ACCESSORIES).
To Polar align using the #883 Deluxe Field Tripod (Fig. 12), follow the instructions provided with the tripod. To Polar
align using the #880 Table Tripod, follow the procedure below.
1. Make sure the viewfinder is aligned with the ETX-90EC (see Aligning the Viewfinder).
2. Remove the two hole covers (13, Fig. 1) from the side of the drive base and thread the two identical fixed
legs (4, Fig. 15) into these holes to a firm feel only.
3. Determine the latitude of the observing location from a road map, atlas, or from the Latitude Chart for Major
Cities of the World; determining the latitude within about one degree is sufficient.
4. The #880 Table Tripod includes two adjustable tripod legs: The standard tripod leg is used at observing
latitudes between 22°and 48.5°and has a dual latitude label attached (Fig. 14). The high-latitude tripod leg
is shorter and is used at observing latitudes between 44°and 66°. Based on the observing latitude
determined in step 3, set aside the tripod leg that is not to be used.
5. Two mounting holes are located on the bottom of the telescope drive base. Mount the appropriate
adjustable tripod leg (as determined in step 4) to the drive base using the following latitudes:
Standard Tripod Leg
o32.5°to 48.5°uses High-Latitude hole (2, Fig. 15).
o22°to 35.5°uses Alternate hole (3, Fig. 15).

High
-
Latitude Tripod Leg
o56°to 66°uses High-Latitude hole.
o44°to 55°uses Alternate hole.
Thread the appropriate leg into the required hole to a firm feel only.
6. A small thumbscrew (6, Fig. 15) is attached to both the standard and high-latitude tripod legs.
Loosening the thumbscrew allows the outer section of the leg to slide over the inner section,
so that the length of the leg can be extended. If using the standard tripod leg, extend the leg
so that the center of the thumbscrew-head is lined up with the latitude of the observing
location on the scale. Then retighten the thumbscrew to a firm feel. (If using the high-latitude
tripod leg, final adjustment of the leg extension is completed in step 9.)
Example: The latitude of New York City is 41°. The tripod leg should be extended so that the
center of the thumbscrew is set next to the 41°reading on the scale.
CAUTION: Polar alignment at latitudes between 22°and 30°requires that the
optional #1422 Low-Latitude Balance Weight (8, Fig. 15) be attached to the
adjustable leg to stabilize the ETX-90EC for observing.
NOTE: With the standard tripod leg threaded into the appropriate hole in the drive
base, the latitude scale may be at an inconvenient position for reading (e.g., the scale
may be facing the drive base). This situation can be remedied by unthreading the leg,
removing the thumbscrew, rotating the inner leg 180°, then reinserting the
thumbscrew. The scale should now be readable when threaded back into the
telescope base.
7. Loosen the vertical and horizontal locks (6 and 10, Fig. 1) and rotate the telescope so that it is
oriented as shown in Fig. 15. Tighten the vertical and horizontal locks. In this orientation the
telescope's optical tube is lined up parallel to the tripod's adjustable leg.
8. Note the dotted line and arrow extending from the telescope tube in Fig. 15. This line defines
the telescope's polar axis. Lift the entire telescope, including tripod, and place the telescope
on a firm and level surface so that this axis is pointing due North. For example, if the location
of Polaris, the North Star, is known then point the telescope directly at Polaris.
9. If using the high-latitude tripod leg in the northern hemisphere, extend the leg until the
telescope's polar axis points to Polaris, or due North, an alignment obtained by sighting along
the telescope tube with the telescope oriented as shown in Fig. 15.
10. NOTE: Observer's located in the earth's
southern hemisphere (e.g., South America,
Australia, etc.) should point the telescope's
polar axis due South.
11. With the telescope now polar-aligned the table
tripod should not be moved, or else polar
alignment will be lost. Motions of the
telescope (e.g., to locate and/or track
objects) should be effected only (a) by
loosening the locks (6 and 10, Fig. 1),
which permits the optical tube to be moved
freely within the telescope mounting, or (b) more
generally, with the locks in their "locked"
positions, by using the arrow keys of the
Electronic Controller.
Fig. 15: Polar Alignment using the #880 Table
Tripod. (1) Standard Tripod Leg with Latitude Scale;
(2) High Latitude Hole; (3) Alternate Hole; (4) Fixed
Tripod Legs; (5) Declination Pointer; (6)
Thumbscrew; (7) R.A. Scale Pointer; (8) optional
#1422 Low
-
Latitude Balance Weight.

Important Note:
For almost all astronomical observing requirements approximate settings of the telescope's
latitude and polar axis are acceptable! Do not allow undue attention to precise polar alignment of the telescope to
interfere with your basic enjoyment of the instrument.
In those unusual cases where more precise polar alignment is desirable, refer to APPENDIX C.
Fig. 16: Locating Polaris.
OBSERVING
OBJECTS IN SPACE
Listed below are some of the many astronomical objects that can be seen with
the ETX-90EC.
The Moon
The Moon is, on average, a distance of 239,000 miles (380,000km) from Earth
and is best observed during its crescent or half phase, when sunlight strikes its
surface at an angle, casting shadows and adding a sense of depth to the view
(Fig. 17). No shadows are seen during a full Moon, causing the overly bright
Moon to appear flat and rather uninteresting through the telescope. Using the
ETX-90EC, brilliant detail can be observed on the Moon, including hundreds of lunar craters and maria, described
below.
Craters are round meteor impact sites covering most of the Moon's surface.
With no atmosphere on the Moon, no weather conditions exist, so the only
erosive force is meteor strikes. Under these conditions, lunar craters can last for
millions of years.
Maria (plural for mare)are smooth, dark areas scattered across the lunar
surface. These dark areas are large ancient impact basins that were filled with
lava from the interior of the Moon by the depth and force of a meteor or comet
impact.
12 Apollo astronauts left their bootprints on the Moon in the late 1960's and early 1970's. However, no telescope
on Earth is able to see these footprints or any other artifacts. In fact, the smallest lunar features that may be seen
with the largest telescope on Earth are about one-half mile across.
NOTE: Except during its early or late crescent phases, the Moon can be an exceptionally bright object to view
through the telescope. To reduce the brightness and glare, use the #905 Variable Polarizing Filter (see OPTIONAL
ACCESSORIES).
Planets
Planets change positions in the sky as they orbit around the Sun. To locate the planets on a given day or month,
WARNING! Never use the
Meade ETX-90EC Astro
Telescope to look at the Sun!
Looking at or near the Sun
will
cause instant andirreversible 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.
Fig. 17: Photo of the Moon shows rich detail
afforded by shadows.

consult a monthly astronomy magazine, such as Sky and Telescope or Astronomy. Listed below are the best
planets for viewing through the ETX-90EC.
Venus is about nine-tenths the diameter of Earth. As Venus orbits the Sun, observers can see it go through phases
(crescent, half, and full) much like those of the Moon. The disk of Venus appears white as sunlight is reflected off
the thick cloud cover that completely obscures any surface detail.
Mars is about half the diameter of Earth, and appears through the telescope as a tiny reddish-orange disk. It may be
possible to see a hint of white at one of the planet's polar ice caps. Approximately every two years, when Mars is
closest to Earth in its orbit, additional detail and coloring on the planet's surface may be visible.
Jupiter is the largest planet in our solar system and is 11 times the diameter of Earth. The planet appears as a disk
with dark lines stretching across the surface. These lines are cloud bands in the atmosphere. Four of Jupiter's 16
moons (Io, Europa, Ganymede, and Callisto) can be seen as "star-like" points of light when using even the lowest
magnification. These moons orbit Jupiter so that the number of moons visible on any given night changes as they
circle around the giant planet.
Saturn is nine times the diameter of Earth and appears as a small, round disk with rings extending out from either
side. In 1610, Galileo, the first person to observe Saturn through a telescope, did not understand that what he was
seeing were rings. Instead, he believed that Saturn had "ears." Saturn's rings are composed of billions of ice
particles ranging in size from a speck of dust to the size of a house. The major division in Saturn's rings, called the
Cassini Division, is generally visible through the ETX-90EC. Titan, the largest of Saturn's 18 moons can also be
seen as a bright, star-like object near the planet.
Deep-Sky Objects
Star charts can be used to locate constellations, individual stars and deep-sky objects. Examples of various deep-
sky objects are given below:
Stars are large gaseous objects that are self-illuminated by nuclear fusion in their core. Because of their vast
distances from our solar system, all stars appear as pinpoints of light, irrespective of the size of the telescope used.
Nebulae are vast interstellar clouds of gas and dust where stars are formed. Most impressive of these is the Great
Nebula in Orion (M42), a diffuse nebula that appears as a faint wispy gray cloud. M42 is 1600 light years from Earth.
Open Clusters are loose groupings of young stars, all recently formed from the
same diffuse nebula. The Pleiades (Fig. 18) is an open cluster 410 light years
away. Through the ETX-90EC several hundred stars are visible.
Constellations are large, imaginary patterns of stars believed by ancient
civilizations to be the celestial equivalent of objects, animals, people, or gods.
These patterns are too large to be seen through a telescope. To learn the
constellations, start with an easy grouping of stars, such as the Big Dipper in
Ursa Major. Then, use a star chart to explore across the sky.
Galaxies are large assemblies of stars, nebulae, and star clusters that are bound by gravity. The most common
shape is spiral (such as our own Milky Way), but galaxies can also be elliptical, or even irregular blobs. The
Andromeda Galaxy (M31) is the closest spiral-type galaxy to our own. This galaxy appears fuzzy and cigar-shaped.
It is 2.2 million light years away in the constellation Andromeda, located between the large "W" of Cassiopeia and
the great square of Pegasus. Under clear, dark conditions, M31 can be seen with the naked eye and is a fascinating
object through the ETX-90EC.
Fig. 18: The Pleiades Star Cluster (M45) in
the constellation Taurus.

PHOTOGRAPHY WITH THE ETX-90EC
Photography through the ETX-90EC requires the addition of the optional #64 T-Adapter (see OPTIONAL
ACCESSORIES). With the #64 T-Adapter attached to the telescope (Fig. 19), through-the-telescope photography is
possible with any 35mm camera body with a removable lens. In this way the telescope effectively becomes the lens
of the camera.
For through-the-telescope photography, turn the flip-mirror control, (5, Fig. 19) to the "down" position, allowing light
to pass straight through the telescope and out the photo port (17, 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. 19) 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 (1250mm focal length): Camera Body + T-Mount + Section
(1) of the #64 T-Adapter (7, Fig. 19). Format 1 utilizes the short
section only of the #64 T-Adapter 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 with a slight darkening at the corners of the 35mm frame (see
Fig. 20).
•Format 2 (1450mm focal length): Camera Body + T-Mount +
Sections (1) and (2) of the #64 T-Adapter (see Fig. 19). Format 2 utilizes both sections of the #64 T-Adapter
threaded together to form a rigid unit as shown in Fig. 19, 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 (see Fig. 21).
To frame an object in the viewfinder of the 35mm camera body, loosen slightly the knurled ring (3, Fig. 19) 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-90EC 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-90EC:
1. Use a rigid tabletop or the optional #883 Deluxe Field Tripod as a platform for the telescope. At effective
focal lengths of 1250mm (Format 1) and 1450mm (Format 2), even small external vibrations can easily ruin
an otherwise good photo.
CAUTION: With the #64 T-Adapter and a camera body mounted to the ETX-90EC photo port, the
telescope can only be rotated vertically 45°. Moving past this point may damage the telescope and
camera.
2. Use a cable-operated shutter release. Touching the camera body to initiate shutter operation will almost
certainly introduce undesirable vibrations.
Fig. 19: Using the #64 T-Adapter. (1) Short
Section of #64 T-Adapter; (2) Extension Section
of #64 T-Adapter; (3) Knurled Attachment Ring;
(4) T-Mount; (5) Flip-Mirror Control in "down"
position; (6) 35mm Camera Body; (7) Inset
shows Format 1.

3. Focus the image with extreme care. While observing the subject through the camera's reflex viewfinder, turn
the ETX-90EC's focus knob (9, Fig. 1) to achieve the sharpest possible focus. Note that some 35mm
cameras may have an optional focusing screen (available from the manufacturer) for use with a long
telephoto lens. This screen provides a brighter and clearer image to focus and is highly recommended.
4. Correct shutter speeds vary widely, depending on lighting conditions and film used. Trial-and-error is the
best way to determine proper shutter speed in any given application.
NOTE: The camera used with the ETX-90EC may have a built-in exposure meter that is still active
when the standard lens is removed and the body is connected to the telescope with the T-Mount. If
used for terrestrial photography, the camera meter should be acceptable. If used for
astrophotography, the meter probably will not provide good results since camera meters are not
made to compensate for a dark sky.
5. Terrestrial photography through the ETX-90EC 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.
6. Photography of the Moon and planets through the ETX-90EC can be especially gratifying, but points 1
through 4 should be particularly noted in this case. Lunar or planetary photography requires that the
telescope be polar aligned (see Polar Alignment Procedure), and that the telescope's motor drive be in
operation (see Electronic Controller Modes).
NOTE: Long exposure photography of deep-sky objects is not practical with the ETX-90EC, since this type
of photography requires special electronic and optical guiding devices not available for this telescope.
Fig. 20: Example of Format 1 Photo
(1250mm).
Fig. 21: Example of Format 2 Photo
(1450mm).

OPTIONAL ACCESSORIES
A wide assortment of professional Meade accessories is available for the ETX-
90EC. Meade accessories greatly extend many important applications to the
telescope, from low-power, wide-field terrestrial viewing to high-power lunar and
planetary observing. The premium quality of these accessories is well-suited to
the quality of the instrument itself.
Meade telescopes and accessories, including optional accessories for ETX-
series telescopes are available at more than 2000 dealer locations in the U.S.
and Canada and through Meade international distributors worldwide.
Eyepieces: Meade Super Plössl (SP), Super Wide Angle (SWA), and Ultra Wide
Angle (UWA) Eyepieces in the standard American-size (1.25") barrel diameter (Fig.
23) permit a wide range of magnifying powers with the ETX-90EC. Powers obtain-
ed with each available eyepiece are shown in the following table:
Eyepiece
Magnifying
Power
with ETX-
90EC
With
#126
2X
Barlow
Lens
SP
6.4mm
195X 390X **
SP
9.7mm
129X 258X
SP
12.4mm
101X 202X
SP 15mm 83X 166X
SP 20mm 63X 126X
SP 26mm
*
48X 96X
SP 32mm 39X 78X
SP 40mm 31X 62X
SWA
13.8mm
91X 182X
SWA
18mm
69X 138X
SWA
24.5mm
51X 102X
UWA
4.7mm
266X N/A
UWA
6.7mm
187X 374X **
* Included as standard
equipment with the ETX-90EC
telescope.
** Use these eyepieces only
under extremely steady
atmospheric conditions.
Fig. 23: Optional eyepieces yield
higher and lower magnifying
powers with the telescope.
Meade Super Plössl and Super Wide Angle Eyepieces are ideal for general-purpose
astronomical or terrestrial observing. The typical ETX-90EC user may wish to add two or
three of these eyepieces to his or her telescope. An introductory selection might include
the SP 9.7mm and SP 15mm eyepieces, while the more advanced observer might select
the SP 9.7mm, SP 12.4mm, and SWA 18mm. Meade Super Wide Angle Eyepieces yield
extrem
ely wide fields of view, perfect for the examination of star fields, diffuse nebulae, or
for terrestrial applications. Under steady seeing conditions Meade UWA 4.7mm and
6.7mm eyepieces present the widest fields of view obtainable at high powers and are
excellent eyepieces for viewing the Moon and planets.
WARNING! Never use the
Meade ETX-90EC Astro
Telescope to look at the Sun!
Looking at or near the Sun
will
cause instant andirreversible 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.

#126 2x Barlow Lens:
An amplifying lens, the #126 2x Barlow Lens (Fig. 24) doubles
the powers of each eyepiece with which it is used. Insert the #126 into the telescope's
eyepiece-
holder first, followed by an eyepiece. Example: By itself the SP 26mm eyepiece
yields a power of 48X with the ETX-90EC; when used in conjunction with the #126 2x
Barlow Lens, this eyepiece yields 96X.
The Meade #126 is an achromatic, high-performance, short-focus Barlow Lens, perfectly
suited to the low-profile design of the ETX-90EC. Lens surfaces are multi-coated for
maximum image contrast and light transmission.
Fig. 24: Use the #126 2x Barlow
Lens to double the magnification
of the eyepiece employed.
Fig. 25: #825 Right-Angle
Viewfinder.
#825 8 x 25mm Right-Angle Viewfinder: Similar in optical characteristics to the 8 x
21mm straight-through viewfinder supplied as standard-equipment with the ETX-90EC,
the #825 right-angle viewfinder (Fig. 25) allows for a comfortable 90°viewing position.
The #825 viewfinder replaces the standard-equipment 8 x 21mm viewfinder and fits into
the same bracket on the telescope.
#64 T-Adapter: The #64 T-Adapter (1, Fig. 26) is the basic means of
photography through the ETX-90EC. The adapter threads to the rear cell of the
telescope, followed by a T-Mount appropriate to your brand of 35mm camera.
With the #64 T-Adapter and T-Mount in place, the camera body is rigidly
coupled to the telescope's optical system, which in effect becomes the camera's
lens.
#880 Table Tripod: Lightweight and extremely portable, the #880 Table Tripod
(2 and 3, Fig. 26) attaches quickly to the telescope drive base and provides a
sturdy platform for astronomical viewing. Two identical fixed tripod legs (3, Fig.
26) mount to holes on the side of the drive base. The adjustable standard tripod
leg (2, Fig. 26), with its two latitude scales, is mounted to one of two holes on
the bottom of the drive base and permits the telescope to be polar aligned for
latitudes between 22°and 48.5°. At higher observing latitudes the shorter high-
latitude tripod leg, also included and shown in Fig. 27, is substituted for the
standard tripod leg.
#1422 Low-Latitude Balance Weight: If the ETX-90EC is to be used with the
#880 Table Tripod and polar-aligned at latitudes below 30°, the telescope can
become unbalanced, particularly if heavier accessories (e.g., a camera body)
are attached to the eyepiece-end of the telescope. The #1422 Low-Latitude
Balance Weight (4, Fig. 26) slides on to the standard tripod leg and enables
rock-solid stability of the telescope even at lower latitudes.
Fig. 26: Astronomical photography with the
ETX. (1) #64 T-Adapter; (2) Standard Tripod
Leg; (3) Fixed Tripod Legs; (4) #1422 Low-
Latitude Balance Weight.
Fig. 27: (1) High-Latitude Tripod Leg; (2)
Thumbscrew Lock.

#883 Deluxe Field Tripod:
Manufactured of strong, lightweight extruded
aluminum, the #883 Deluxe Field Tripod (Fig. 28) allows standing or seated
observations through the ETX-90EC. Tripod height is continuously adjustable
from 34" to 54". Micrometric controls in both azimuth and elevation-angle permit
precise polar alignment of the telescope's fork mount for astronomical
applications. Designed exclusively for ETX-series astronomical telescopes, the
#883 Deluxe Field Tripod includes all the rigidity and stability required for high-
power observing through the telescope. For terrestrial observing, where
altazimuth orientation of the telescope is desirable, the tripod head tilts and
locks at 90°(inset, Fig 28).
#882 Standard Field Tripod: (not shown) If the ETX-90EC is used primarily for
terrestrial observing and less-extensively for astronomical viewing, the polar
alignment capability of the #883 Deluxe Field Tripod may not be required. In this
case the #882 Standard Field Tripod provides a rigid observing platform for the
telescope in the altazimuth (Alt/Az) configuration, only. Alternately, if the
telescope is equipped with the optional #497 ETX Autostar Computer Controller,
astronomical sidereal-rate tracking can be effected in the Alt/Az configuration
permitted with the #882 Standard Field Tripod, without any requirement for polar alignment. The #882 Standard
Field Tripod is variable in height between 34" and 54" for seated or standing observing through the telescope.
#932 45°Erecting Prism: If the ETX-90EC is to be used for extensive
terrestrial applications, the #932 45°Erecting Prism (1, Fig. 29) is a
useful accessory. Images through the 90°eyepiece-holder (4, Fig. 1)
appear right-side-up, but reversed left-for-right. The #932 Prism threads
on to the telescope's photo port (17, Fig. 1) and presents a correctly
oriented image as well as a convenient 45°observing angle. An eyepiece
of any focal length (magnifying power) may be inserted into the #932
Prism. Note that the flip-mirror control (4, Fig. 29) must be in the "down"
position for use with the #932 Prism.
Important Note: In the most discriminating applications, such as in
observing delicate bird feather-structure at long distance, the ETX-90EC's
internal, optically-flat mirror yields a higher-resolution image than is
possible with any prism, including the #932. In these special cases ETX-
90EC users are advised to observe with the eyepiece in the standard 90°
eyepiece-holder (as shown in Fig. 1), 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 well-trained to observe
very fine detail. In typical terrestrial applications, no image differences between the two eyepiece locations can
generally be noted.
#765 Soft Carrying Bag: Perfectly suited to field use of, or traveling with, the
telescope, the soft-padded, Cordura-type #765 Soft Carrying Bag (Fig. 30) for
the ETX-90EC includes a shoulder strap and permits ready transport of the
complete telescope, including the table tripod, eyepieces, and other
accessories. With the #765 Soft Carrying Bag the telescope can go anywhere
with you at a moment's notice.
Fig. 30: The #765 Soft Carrying Bag.
Fig. 28: The #883 Deluxe Field Tripod with
ETX-90EC Telescope, set up in the Alt/Az
configuration (tripod head locked at 90°), for
terrestrial applications. (Inset) Tripod head
tilted for polar alignment.
Fig. 29: The #932 45°Erecting Prism threaded to the
rear cell of the ETX-90EC. (1) #932 45°Erecting
Prism; (2) Eyepiece; (3) Knurled Lock-ring; (4) Flip-
Mirror Control.

Fig. 31: #774 Hard Carrying Case.
#774 Hard Carrying Case: For situations that require ruggedness and
portability, the #774 Hard Carrying Case (Fig. 31) provides a secure
environment for the ETX-90EC. The fitted foam interior protects the telescope
while providing ample room for additional eyepieces, a table tripod, the
Electronic Controller, ETX Autostar, and much more.
#607 DC Power Cord: To power the ETX-90EC from an automobile cigarette
lighter plug, the #607 DC Power Cord (Fig. 32) is required. Supplied with 25 ft.
cord.
Fig. 32: #607 DC Power Cord.
#541 AC Adapter: (not shown) The #541 AC Adapter permits powering of the ETX-90EC via a standard household
(115vAC) electrical outlet. Supplied with 25 foot cord.
#1244 Electric Focuser: The #1244 Focuser (Fig. 33) replaces the manual
focuser knob of the ETX-90EC and permits smooth, precise electric focusing of
the image through a remote handbox supplied with the focuser. Alternately, on
the ETX-90EC, the #1244 Focuser may be plugged into the telescope's
computer control panel and operated through either the Electronic Controller or
the optional #497 ETX Autostar Computer Controller.
Fig. 33: #1244 Electric Focuser.
Fig. 34: (1) #905 Variable Polarizing Filter;
(2) Eyepiece.
#905 Variable Polarizing Filter: For glare reduction in observing the Moon the
#905 Variable Polarizer (Fig. 34) includes two Polarizer filters mounted in a
specially-machined cell. The #905 permits variable settings of light transmission
between 5% and 25%, to account for varying lunar surface brightness according
to the phase of the Moon. Accepts 1.25" barrel-diameter eye-pieces of any focal
length.

Epoch 2000sk Sky Software:
Meade Epoch 2000sk astro-nomical
software (Fig. 35) has created a revolution in the way amateur
astronomers prepare for observing sessions at the tele-scope. For
Epoch 2000sk presents on the display of a personal computer an
incredibly detailed simulation of the entire sky, including up to 281,000
celestial objects. Epoch 2000sk allows the presentation of the most
complex star fields just as they actually appear through the telescope.
And yet, notwithstanding its precision and detail, Epoch 2000sk is easy
and intuitive to use, even by the novice. Epoch 2000sk operates the
ETX-90EC through a laptop computer in the field using the #497
Autostar Computer Controller and #505 Connector Cable Set. Epoch
2000sk astronomical software is available in the following formats:
•Epoch 2000sk-JR: 10,000 objects supplied on 3.5" discs for Windows 3.1 or higher, or Windows 95.
•Epoch 2000sk Sky Software: 281,000 objects supplied on 3.5" discs for Windows 3.1 or higher, or
Windows 95.
•Epoch 2000sk-CD Sky Software: Over 19 million objects supplied on CD-ROM for Windows 3.1 or higher,
or Windows 95.
Fig. 35: Epoch 2000sk software

MAINTENANCE AND SERVICING
General Maintenance
The ETX-90EC is a precision optical instrument designed to yield a lifetime of
rewarding applications. Given the care and respect due any precision instrument,
the ETX-90EC 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 gentle strokes of a camel hair brush or blown off with an ear syringe
(available at any pharmacy). Do not use a commercial photographic lens cleaner.
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. A single drop of biodegradable dishwashing soap may be added per pint
of solution. Use soft, white facial tissues and make short, gentle strokes. Change tissues often.
CAUTION: Do not use scented, colored, 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 3 may be used to clean the inside
surface of the lens.
CAUTION: Do not touch the aluminized circular surface of the secondary mirror with a finger, a
tissue, or any other object. Scratching of the mirror surface will 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-90EC is used outdoors on a humid night, telescope surfaces may accumulate water
condensation. 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 being packed away. Do not,
however, wipe any of the optical surfaces. Rather, simply allow the telescope to sit for some time in warm
indoor air, so that the wet optical surfaces can dry unattended. In addition, the dust cap should not be
placed back on to the optical tube until the telescope is thoroughly dry.
6. If the ETX-90EC is not to be used for an extended period, perhaps for one month or more, it is advisable to
remove the eight AA-size batteries from inside the drive base. Batteries left installed for prolonged periods
may leak, causing damage to the telescope's electronic circuitry (see Assembly Instructions).
7. The super-gloss anodized finish of the ETX-90EC's deep-violet optical tube fades if left in direct sunlight for
prolonged periods.
8. Do not leave the ETX-90EC telescope outdoors on a warm day or inside a sealed car for an extended
period of time; excessive ambient temperatures can damage the telescope's internal lubrication and
electronic circuitry.
9. A set of two (English-format) hex wrenches is provided with each ETX-90EC Astro Telescope. These
wrenches are used as follows:
oSmall wrench (.05"): Use the small wrench to tighten the set-screws of any knobs which may
loosen (e.g., the focus knob or flip-mirror control knob).
oMedium wrench (1/16"): This wrench is used to detach the viewfinder bracket from the telescope's
rear-cell.
WARNING! Never use the
Meade ETX-90EC Astro
Telescope to look at the Sun!
Looking at or near the Sun
will
cause instant andirreversible 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.

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 with the vertical and horizontal locks (6 and 10, Fig. 1) in
the unlocked positions. 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 objective lens. It is highly recommended to use the #765 Soft Carrying Bag or #774 Hard
Carrying Case to transport the telescope (see OPTIONAL ACCESSORIES).
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 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.
Troubleshooting
The following suggestions may be helpful if there are difficulties with operation of the Electronic Controller or ETX-
90EC telescope.
The power indicator light does not come on or there is no response when pressing the Electronic Controller
arrow keys:
•Verify that the computer control panel power switch (1, Fig. 4) is in the ON position.
•Verify that the Electronic Controller cord (4, Fig. 5) is firmly connected to the HBX port (3, Fig. 4).
•If using internal power (batteries), verify that the batteries are installed correctly and that they have sufficient
charge (see Assembly Instructions).
NOTE: If the batteries are getting low on charge there will be a marked difference in the slew speed. The
speed indicator lights may also flash and the speed may change. If any of these symptoms occurs, turn the
power off and replace the batteries.
•If using an external power source, verify that it is properly connected between the 12 volt connector (4, Fig.
4) and either a wall plug (AC source) or a car lighter (DC source).
•If the Electronic Controller does not respond to commands, place the power switch to OFF and then back to
ON.
•If the telescope does not slew after power is applied or if the motor quits or stalls, verify that there are no
physical obstructions that would impede telescope movement.
•If all physical obstacles are removed and the telescope still does not move properly, turn off the power and
unplug the Electronic Controller. Plug the Electronic Controller back in and turn the power back on.
Unable to see an image through the eyepiece:
•Confirm that the lens cover has been removed from the telescope.
•Confirm that the flip-mirror control (16, Fig. 1) is in the "up" position if using the eyepiece holder (4, Fig. 1)
so that light is directed to the eyepiece (1, Fig. 1). Confirm that the flip-mirror control is in the "down"
position if using the #932 Erecting Prism or doing photography with the ETX-90EC (see Telescope
Controls andPHOTOGRAPHY WITH THE ETX-90EC).

Object appears in the viewfinder but not in the eyepiece:
•The viewfinder is not properly aligned with the telescope (see THE VIEWFINDER).
Slew speed does not change when the SPEED key is pressed or the telescope moves slowly even though
the fast slew speed is chosen:
•Verify that only one light is lit on the Electronic Controller. If more than one light is on or blinking then the
Mode function is active. Exit the Mode function by pressing and holding the MODE key until only one light is
on (seeElectronic Controller Modes).
•The battery power may be low (see Assembly Instructions.)
Telescope does not track a celestial object:
•The telescope can only track celestial objects automatically if it is properly polar aligned and the motor drive
has been activated (see Polar Alignment Procedure and Modes of Operation).
Images through the eyepiece appear unfocused or distorted:
•The magnification used may be too high for the seeing conditions. Back off to a lower power eyepiece
(seeUnderstanding Magnification).
•If inside a warm house or building, move outside. Interior air conditions may distort terrestrial or celestial
images, making 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.
•If viewing a land object on a warm day, heat waves will distort the image (see Terrestrial Observing).
•For clear viewing of objects, turn the focus knob (9, Fig. 1) slowly since the "in-focus" point of a telescope is
precise. Turning the focus knob too quickly may cause the focus point to pass without notice.
•The optics within the telescope need time to adjust to the outside ambient temperature to provide the
sharpest image. To "cool down" the optics, set the telescope outside for 10 to 15 minutes before observing
begins.
Telescope moves off a terrestrial object while observing:
•The motor drive may be activated (see Modes of Operation).
•Verify that the vertical and horizontal locks are tight (see Telescope Controls).
Telescope does not move past a certain point:
•The built-in vertical or horizontal rotational "stops" may have been reached (see Rotational Limits).
Telescope pauses when changing slew direction:
•This pause is normal (see Arrow Keys).
A terrestrial object appears reversed left-for-right:
•An eyepiece in the standard 90°observing position (4, Fig. 1) yields this image orientation. To view a
correctly oriented image, the optional #932 Erecting Prism is required (see OPTIONAL ACCESSORIES.
Meade Customer Service
If you have a question concerning the ETX-90EC, call the Meade Instruments Customer Service Department at
[phone], or fax at [phone]. Customer Service hours are 8:30 AM to 4:30 PM, Pacific Time, Monday
through Friday. In the unlikely event that the ETX-90EC 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.
Specifications: ETX
-
90EC Telescope
Optical design
Maksutov-Cassegrain
Primary mirror diameter
96mm (3.78")
Clear aperture
90mm (3.5")
Focal length
1250mm
Focal ratio (photographic speed) f/13.8
Near focus (approx)
11.5 ft (3.5m)
Resolving power
1.3 arc secs
Super multi
-
coatings
standard
Limiting visual stellar magnitude (approx)
11.7
Image scale
1.16°/inch
Maximum practical visual power
325X
Optical tube dimensions (dia. x length)
10.4cm x 27.9cm (4.1" x 11")
Secondary mirror obstruction (dia.; %)
27.9mm (1.1"); 9.6%
Telescope mounting
fork type; double tine
Setting circle diameters
Dec: 3.5"; RA: 7"
Input voltage
12-volts DC
Hemispheres of operation
north and south, switchable
Electronic controller
4 speed, both axes
Bearings:
Altitude
UHMW Polyethylene
Azimuth
PTFE
Materials:
Tube body
aluminum
Mounting high-impact ABS, aluminum-reinforced
Primary mirror
Pyrex® glass
Correcting lens
BK7 optical glass, Grade-A
Telescope dimensions
38cm x 18cm x 22cm (15" x 7" x 9")
Telescope net weight: (incl. Electronic Controller & batteries)
3.5kg (7.8 lbs)
Telescope shipping weight
5.6kg (12.3 lbs)

PRECISE POLAR ALIGNMENT; SETTING CIRCLES
Precise Polar Alignment
Important note: For almost all astronomical observing requirements approximate
settings of the telescope's latitude and polar axis are acceptable! Do not allow
undue attention to precise polar alignment of the telescope to interfere with your
basic enjoyment of the instrument.
If desired, more precise polar alignment may be obtained by first accomplishing
basic polar alignment as detailed in Polar Alignment Procedure, then returning to
this procedure:
NOTE: This procedure moves the telescope physically to precisely line up with
the celestial pole. Do not use the Electronic Controller arrow keys to move the
telescope electronically or polar alignment will be lost.
1. Orient the entire telescope, including tripod or tripod legs, so that the polar axis is pointing toward Polaris
(Fig. 15).
2. While observing through the SP 26mm eyepiece of the telescope, adjust the length of the adjustable tripod
leg until Polaris is visible in the eyepiece. Use a combination of (a) lifting and turning the entire telescope (or
nudging the position of one of the fixed tripod legs) and (b) adjusting the length of the adjustable tripod leg
to place Polaris in the center of the telescope's field.
3. Repeat step 2 of this procedure in about 15 minutes to see how much drift has taken place and to make the
alignment more precise.
Although the above procedure is somewhat tedious (since the field of view of the telescope with the SP 26mm
eyepiece is only about 1°), it is a worthwhile effort if precise polar alignment is desired (e.g., if photography of the
Moon or a planet is to be performed). With Polaris placed in the center of the telescope's eyepiece, the telescope is
now polar aligned within about one or two degrees - a level of alignment precision more than sufficient for almost
any observing application.
To provide the most stable platform from which to polar align the ETX-90EC it is recommended to purchase
the #883 Deluxe Field Tripod. The tripod head tilts easily to the local latitude angle for quick polar alignment, and
locks in a 90°position to facilitate Alt/Az viewing (see OPTIONAL ACCESSORIES).
Setting Circles
The ETX-90EC is equipped with R.A. and Dec Setting Circles (14 and 18, Fig. 1) to aid in locating faint celestial
objects when the telescope has been polar aligned. Setting circles emulate the celestial coordinates found on star
charts or in sky catalogs. Any charted object is easily located by coordinates in R.A. (in hours, minutes, and
seconds, from 0h 0m 0s to 23h 59m 59s and Dec (in degrees from 0°to ±90°).
With the ETX-90EC polar aligned the Electronic Controller arrow keys (1, Fig. 5) are used to move the telescope in
Right Ascension (left and right keys) and Declination (up and down keys).
NOTE: The Dec setting circle is located on the left arm of the telescope fork mount. The right arm of the mount
contains a graduated circle (mounted behind the knurled knob of the vertical lock), without Declination numbers.
•Right Ascension Setting Circle: Since celestial objects move
in Right Ascension the R.A. setting circle (Fig. 36) must be
reset as each object is located during an observing session.
The R.A. pointer is located on the drive base 90°
counterclockwise from the telescope's computer control panel (11, Fig. 1) immediately under the R.A. circle.
NOTE: The R.A. circle has two rows of numbers from 0 to 23, corresponding to the hours of a 24-hour clock. The
upper row of numbers is used by observers in the Earth's northern hemisphere, the lower row by observers in the
Earth's southern hemisphere.
WARNING! Never use the
Meade ETX-90EC Astro
Telescope to look at the Sun!
Looking at or near the Sun
will
cause instant andirreversible 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.
Fig. 36: Section of Right Ascension setting circle.

•
Declination Setting Circle: The Dec setting circle (Fig. 37) has been
factory set to read the correct Declination of sky objects. Since the
smooth knob on this fork mount arm need never be loosened, the Dec
setting circle should always remain calibrated.
If for some reason this knob becomes loose and the Dec setting circle
must be recalibrated, level the optical tube (5, Fig. 1) so that it is
parallel to the drive base. Loosen the smooth knob covering the Dec setting circle until the setting circle
moves freely. Reposition the setting circle so that the "0" setting is lined up with the Dec pointer (5, Fig. 15).
Retighten the Dec knob.
To use the setting circles to find astronomical objects, the ETX-90EC must first be polar aligned; it is advisable that
the motor drive be turned on (see Modes of Operation, page 11) and that a low-power eyepiece (e.g., the SP 26mm
eyepiece) be employed. Then follow this procedure:
1. Identify the celestial coordinates (R.A. and Dec) of a bright, easy-to-find object, such as a bright star. (Avoid
using Polaris or any object near Polaris.) Coordinates of some bright stars are listed in the Star Locator
(page 22), or use a star chart. Center this object in the telescope's field of view.
2. Manually turn the R.A. circle (14, Fig. 1) to read the R.A. of the object at the R.A. pointer (7, Fig. 15).
3. The R.A. circle is now calibrated to read the correct R.A. of any object at which the telescope is pointed.
The Dec circle is already calibrated through polar alignment.
4. To find another object, again identify the R.A. and Dec coordinates. Then, without touching the setting
circles, move the telescope (manually, by unlocking the vertical and horizontal locks, or by slewing the
telescope using the Electronic Controller arrow keys) so that the R.A. and Dec pointers read the coordinates
of the second object.
5. If the above procedure has been followed carefully, the second object will now be in the telescope's field of
view.
NOTE: Since the second object (i.e., the object to be located) is in constant motion, once the R.A. circle is calibrated
(step 2 above) the telescope should be moved rapidly to read the coordinates of the second object. Otherwise the
second object will no longer be in the position indicated by the R.A. circle.
Using setting circles requires a developed technique. When using the circles for the first time, try hopping from one
bright star (the calibration star) to another bright star of known coordinates. Practice moving the telescope from one
easy-to-find object to another. In this way the precision required for accurate object location becomes evident.
Fig. 37: Section of Declination setting circle.

ROADMAP TO THE STARS
The night sky is filled with wonder and intrigue. You too, can enjoy exploring the
universe simply by following a few pointers on a roadmap to the stars.
First, find the Big Dipper which is part of the constellation Ursa Major. The Big
Dipper is usually easy to locate year round in North America due to its proximity
to the North Star, Polaris.
Extending directly out from the far side of the Big Dipper's cup is the constellation
Orion. One of the most exquisite areas of the winter sky, Orion is distinguished
by two bright stars, Rigel and Betelgeuse, and Orion's belt which is marked by
three stars in a row. The Orion Nebula is located south of the belt and is one of
the most observed deep-sky objects by amateur astronomers.
Extending from the "pointer stars" - or end stars - of
the Big Dipper's cup is Polaris, the closest star to the
northernmost point of the celestial sphere. Extending
from Polaris is the Great Square shared by the
constellation Pegasus and Andromeda. Within
Andromeda is the Andromeda Galaxy, the closest
large galaxy to our solar system at about 2.2 million
light-years away.
The Summer Triangle is a notable region in the sky to
the left of the handle of the Big Dipper. The triangle is
made up of three very bright stars: Vega, Deneb and
Altair.
By drawing an imaginary line outward from the handle
of the Big Dipper you reach the southern
constellation"Scorpius." Scorpius curves to the left
like the tail of a scorpion in the sky, or like letter "J."
Amateur astronomers commonly use the phrase "Arc
to Arcturus and spike to Spica" to refer to the area
directly off the arc in the handle of the Big Dipper.
Follow the arc to Arcturus, the second brightest star in
the Northern Hemisphere, then spike down to Spica,
the 16th brightest star in the sky. Now follow the arc in
the handle of the Big Dipper in the opposite direction
and you reach another famous arc called The Sickle,
in the constellation Leo.
WARNING! Never use the
Meade ETX-90EC Astro
Telescope to look at the Sun!
Looking at or near the Sun
will
cause instant andirreversible 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.
Fig. 38: Road Map to the Stars.

YOU AND THE UNIVERSE
Distance from the Earth to the Moon
Distance between planets
Distance of the Earth to the Sun is 93 million miles or 1 Astronomical Unit (AU)
Distance between stars
Distance from the Sun to the nearest star is about 4.3 light years, or 25 trillion miles. This distance is so large that if
a scale model were created with the Earth one inch away from the Sun, the nearest star would have to be placed
over 4 miles away!
Approximately one hundred billion stars, including the Sun, comprise the Milky Way Galaxy, which is a spiral-
shaped collection of stars believed to be more than 100,000 light years in diameter.
Distance between galaxies
Related Topics: