Celestron AstroMaster 102AZ User manual

INSTRUCTION MANUAL
22065 AstroMaster 102AZ
ENGLISH
TELESCOPE
102A Z
102 MM REFRACTOR

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TABLE OF CONTENTS
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
ASSEMBLY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Setting up the Tripod . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Moving the Telescope Manually. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Installing the Telescope Tube to the Mount. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Installing the Diagonal & Eyepieces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
TELESCOPE BASICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Image Orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Focusing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Aligning the Finderscope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Calculating Magnification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Determining Field of View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
General Observing Hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
ASTRONOMY BASICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
CELESTIAL OBSERVING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Observing the Moon. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Observing the Planets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Observing the Sun . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Observing Deep Sky Objects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Star Hopping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Seeing Conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
ASTROPHOTOGRAPHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Planetary & Lunar Photography with Special Imagers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Terrestrial Photography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
TELESCOPE MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Care and Cleaning of the Optics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
OPTIONAL ACCESSORIES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
AstroMaster Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

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INTRODUCTION
Congratulations on your purchase of an AstroMaster series telescope. Your AstroMaster
series is made of the highest quality materials to ensure stability and durability. With proper
care, your telescope will provide a lifetime of pleasure with a minimal amount of
maintenance.
The AstroMaster series features a compact and portable design with ample optical performance to introduce any
newcomer to the exciting world of amateur astronomy. In addition, your AstroMaster telescope is ideal for terrestrial
observations with superb high power viewing.
AstroMaster telescopes carry a two year limited warranty. For details see our website at www.celestron.com
Your AstroMaster features
• All coated glass optical elements for clear, crisp images.
• Smooth functioning, rigid alt-azimuth mount with a large pan handle with built-in clutch for easy targeting.
• A preassembled tripod with 1.25-inch steel legs, which provides a stable platform.
• Quick and easy no-tool set up.
• TheSkyX-First Light Edition astronomy software with information about celestial objects and printable sky maps.
• Terrestrial and astronomical observing capability.
Read this manual carefully before embarking on your journey through the Universe. It may take a few observing sessions
to become familiar with your telescope, so keep this manual handy until you have fully mastered your telescope’s operation.
The manual provides detailed instructions, reference material and helpful hints guaranteed to make your observing
experience as simple and pleasurable as possible.
Your telescope is designed to give you years of fun and rewarding observations. However, there are a few things to
consider before using your telescope to ensure your safety and protect your equipment.
SOLAR WARNING
Never look directly at the Sun with the naked eye or with a telescope unless you have the proper solar filter. Permanent and irreversible eye damage may result.
Never use your telescope to project an image of the Sun onto any surface. Internal heat build-up can damage the telescope and any accessories attached to it.
Never use an eyepiece solar filter or a Herschel wedge. Internal heat build-up inside the telescope can cause these devices to crack or break, allowing unfiltered sunlight to
pass through to the eye.
Do not leave the telescope unsupervised, especially when children or adults unfamiliar with the correct operating procedures of your telescope are present.

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1. Objective Lens 7. Pan Handle
2. Telescope Optical Tube 8. Accessory Tray
3. Red Dot Finder 9. Tripod
4. Eyepiece 10. Azimuth Lock
5. Diagonal 11. Alt-Az Mount
6. Focus Knob 12. Dovetail Mounting Bracket
Fig. 1
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10
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ASSEMBLY
Set up your telescope indoors the first time before attempting to assemble it outdoors.
Each AstroMaster comes in one box. The pieces in the box are: altazimuth mount with attached pan handle,10 mm 1.25”
eyepiece, 20 mm 1.25” eyepiece, 1.25” erect image diagonal, “TheSkyX-First Light Edition astronomy software”.
SETTING UP THE TRIPOD
1. Remove the tripod from the box (Figure 2-1). The tripod comes preassembled.
2. Stand the tripod upright and pull the tripod legs apart until each leg is fully extended and then push down slightly on the
tripod leg brace (Figure 2-2).
3. Next, we will install the tripod accessory tray (Figure 2-3) onto the tripod leg brace (center of Figure 2-2).
Hold the tray flat side facing down. Align the center of the tray to match the center of the tripod brace and push down
slightly (Figure 2-4).
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Fig. 2-1 Fig. 2-2 Fig. 2-3 Fig. 2-4
4. Rotate the tray until the ears are under the leg brace support of each leg and push slightly. They will lock in place (Figure
2-5). The tripod is now completely assembled (Figure 2-6).
5. You can extend the tripod legs to the height you desire. At the lowest level the height is 24” (61 cm) and extends to
41” (104 cm). Unlock the tripod leg lock knob at the bottom of each leg (Figure 2-7) and pull the legs out to the desired
height. Then, lock the knob securely. A fully-extended the tripod looks like the image in Figure 2-8. Keep in mind that the
tripod is the most stable and rigid at the lowest height.
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Fig. 2-5 Fig. 2-6 Fig. 2-7 Fig. 2-8

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MOVING THE TELESCOPE MANUALLY
The AstroMaster Alt-Az mount is easy to move wherever you want to point it. The up-and-down (altitude) motion is
controlled by the pan handle (Figure 2-10). The side-to-side (azimuth) motion is controlled by the azimuth lock
(Figure 2-9). To loosen the pan handle and azimuth lock, turn them counterclockwise. When loose, point the telescope to
the desired object, then lock the controls in place by turning them clockwise.
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Fig. 2-9 Fig. 2-10
INSTALLING THE TELESCOPE TUBE TO THE MOUNT
The telescope optical tube attaches to the mount via a dovetail slide bar mounting bracket at the top of the mount (Figure
2-11). For 102AZ refractors, the mounting bar is attached along the bottom of the telescope tube. Before you attach
the optical tube, make sure that the pan handle and azimuth lock are fully locked. Then, put the dovetail bracket in the
horizontal position as shown in Figure 2-12. This will ensure that the mount does not move suddenly while attaching the
telescope optical tube. Also, remove the objective lens.
To mount the telescope tube:
1. Remove the protective paper covering the optical tube.
2. Loosen the mounting knob and the mounting safety screw on the side of the dovetail mounting platform so they do not
protrude into the mounting platform (Figure 2-12).
3. Slide the dovetail mounting bar into the recess on the top of the mounting platform (Figure 2-12).
4. Tighten the mounting knob on the dovetail mounting platform to hold the telescope in place.
5. Hand tighten the mounting platform safety screw until the tip touches the side of the mounting bracket.
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Fig. 2-11 Fig. 2-12 Mounting Knob & Safety Screw in the dovetail bracket

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INSTALLING THE DIAGONAL & EYEPIECES
The diagonal is a prism that diverts the light at a right angle to the light path of the refractor. This allows you to observe in
a position that is more comfortable than looking straight through. This diagonal is an erect image model that corrects the
image to be right side up and oriented correctly left-to-right which is much easier to use for terrestrial observing. Also, the
diagonal can be rotated to any position which is most favorable for you. To install the diagonal and eyepieces:
1. Insert the small barrel of the diagonal into the 1.25” eyepiece adapter of the focus tube on the refractor (Figure 2-13).
Make sure the two thumbscrews on the eyepiece adapter do not protrude into the focuser tube before installation and
the plug up cap is removed from the eyepiece adapter.
2. Put the chrome barrel end of one of the eyepieces into the diagonal and tighten the thumb screw. Again, make sure the
thumbscrew is not protruding into the diagonal before inserting the eyepiece.
3. The eyepieces can be changed to other focal lengths by reversing the procedure in step 2 above.
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Fig. 2-13

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TELESCOPE BASICS
A telescope is an instrument that collects and focuses light. The nature of the optical design determines how the light is
focused. Some telescopes, known as refractors, use lenses, other telescopes, known as reflectors (Newtonians), use
mirrors.
Developed in the early 1600s, the refractor is the oldest telescope design. It derives its name from the method it uses
to focus incoming light rays. The refractor uses a lens to bend or refract incoming light rays, hence the name (see Figure
3-1). Early designs used single element lenses. However, the single lens acts like a prism and breaks light down into
the colors of the rainbow, producing a phenomenon known as chromatic aberration. To get around this problem, a
two-element lens, known as an achromat, was introduced. Each element has a different index of refraction allowing two
different wavelengths of light to be focused at the same point. Most two-element lenses, usually made of crown and flint
glasses, are corrected for red and green light. Blue light may still be focused at a slightly different point.
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cutawayviewofthelightpathofthe
Refractor
Refractor
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IMAGE ORIENTATION
The image orientation changes depending on how the eyepiece is inserted into the telescope. When using a star diagonal
with refractors, the image is right-side-up, but reversed from left-to-right (i.e., mirror image). If inserting the eyepiece
directly into the focuser of a refractor (i.e., without the diagonal), the image is upside-down and reversed from left-to-right
(i.e., inverted). However, when using the AstroMaster refractor and the standard erect image diagonal, the images is
correctly oriented in every aspect.
Image orientation as seen with the unaided
eye and using erecting devices on refractors
and Newtonians
Reversed from left to right, as viewed using
a Star Diagonal on a refractor
Inverted image, normal with Newtonians and
as viewed with eyepiece directly in a refractor
Fig. 3-1 A cutaway view of the light path of the Refractor optical
Fig. 3-2

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FOCUSING
To focus your refractor, simply turn the focus knob located directly below the eyepiece holder (see Figure 1). Turning the
knob clockwise allows you to focus on an object that is farther than the one you are currently observing. Turning the knob
counterclockwise from you allows you to focus on an object closer than the one you are currently observing.
NOTE: If you wear corrective lenses (specifically glasses), you may want to remove them when observing with an eyepiece attached to the telescope. However, when using a camera you
should always wear corrective lenses to ensure the sharpest possible focus. If you have astigmatism, corrective lenses must be worn at all times.
ALIGNING THE RED DOT FINDER
The red dot finder is the quickest and easiest way to point your telescope exactly at a desired object in the sky. It’s like
having a laser pointer that you can shine directly onto the night sky. The red dot finder is a zero magnification pointing tool
that uses a coated glass window to superimpose the image of a small red dot onto the night sky. With both eyes open,
look through the red dot finder and simply move your telescope until the red dot, seen through the red dot finder, merges
with the object as seen with your unaided eye. The red dot is produced by a light-emitting diode (LED); it is not a laser
beam and will not damage the glass window or your eye. The red dot finder is powered by a long life 3-volt lithium battery
(#CR1620) see Figure 3-3. Like all finderscopes, the red dot finder must be properly aligned with the main telescope
before it can be used. The alignment procedure is best done at night since the LED dot will be difficult to see during the day.
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Fig. 3-3 Fig. 3-4
To align the red dot finder:
1. To turn on the red dot finder, turn the switch to the “on” position (Figure 3-3).
2. Locate a bright star or planet and center it in a low power eyepiece in the main telescope.
3. With both eyes open, look through the glass window at the alignment star. If the red dot finder is perfectly aligned, you
will see the red LED dot overlap the alignment star. If the red dot finder is not aligned, take notice of where the red dot
is relative to the bright star.
4. Without moving the main telescope, turn the red dot finder’s two adjustment screws until the red dot is directly over the
alignment star. Experiment as to which way each screw moves the red dot.
5. The red dot finder is now ready for use. Always turn the power off after you have found an object. This will extend the
life of both the battery and the LED.
NOTE:Your battery may already be installed. If not, open the battery compartment (Figure 3-3) with a thin coin or screwdriver. Put the battery in with the “+” sign facing out. Then, put the
battery compartment back on. If you ever need to replace the battery, it is a 3-volt lithium type # CR 1620.
NOTE:The above procedure applies for astronomical observation. But if your finderscope is aligned properly, you can also use it for terrestrial applications. The finderscope acts like a
sighting tube. The red dot may be difficult to see in the daytime, but the dot will let you align objects before looking through the main telescope optics and can be quite helpful.
NOTE:If you plan on storing the telescope for a long period of time, remove the battery to prevent discharge.
Battery
Compartment On/Off Switch

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CALCULATING MAGNIFICATION
You can change the power of your telescope just by changing the eyepiece (ocular). To determine the magnification of
your telescope, simply divide the focal length of the telescope by the focal length of the eyepiece used. In equation format,
the formula looks like this:
Focal Length of Telescope (mm)
Magnification = ______________________________
Focal Length of Eyepiece (mm)
Let’s say, for example, you are using the 20 mm eyepiece that came with your telescope. To determine the magnification
you simply divide the focal length of your telescope (the AstroMaster 102AZ for this example has a focal length of 660
mm) by the focal length of the eyepiece, 20 mm. Dividing 660 by 20 yields a magnification of 33 power.
Although the power is variable, each instrument under average skies has a limit to the highest useful magnification. The
general rule is that 60 power can be used for every inch of aperture. For example, the AstroMaster 90AZ is 4 inches in
diameter. Multiplying 4 by 60 gives a maximum useful magnification of 240 power. Although this is the maximum useful
magnification, most observing is done in the range of 20 to 35 power for every inch of aperture which is 80 to 140 times
for the AstroMaster 102AZ telescope. You can determine the magnification for your telescope the same way.
DETERMINING FIELD OF VIEW
Determining the field of view is important if you want to get an idea of the angular size of the object you are observing.
To calculate the actual field of view, divide the apparent field of the eyepiece (supplied by the eyepiece manufacturer)
by the magnification. In equation format, the formula looks like this:
Apparent Field of Eyepiece
True Field = _________________________
Magnification
As you can see, before determining the field of view, you must calculate the magnification. Using the example in the
previous section, we can determine the field of view using the same 20 mm eyepiece that is supplied standard with
the AstroMaster 102AZ telescope. The 20 mm eyepiece has an apparent field of view of 50°. Divide the 50° by the
magnification, which is 33 power. This yields an actual field of 1.5°.
To convert degrees to feet at 1,000 yards, which is more useful for terrestrial observing, simply multiply by 52.5.
Continuing with our example, multiply the angular field of 1.5° by 52.5. This produces a linear field width of 78.75 feet at a
distance of one thousand yards.

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GENERAL OBSERVING HINTS
When working with any optical instrument, there are a few things to remember to ensure you get the best possible image.
• Never look through window glass. Glass found in household windows is optically imperfect, and as a result, may vary in
thickness from one part of a window to the next. This inconsistency can and will affect the ability to focus your telescope.
In most cases, you will not be able to achieve a truly sharp image, while in some cases, you may actually see a double
image.
• Never look across or over objects that are producing heat waves. This includes asphalt parking lots on hot summer days
or building rooftops.
• Hazy skies, fog, and mist can also make it difficult to focus when viewing terrestrially. The amount of detail seen under
these conditions is greatly reduced.
• If you wear corrective lenses (specifically glasses), you may want to remove them when observing with an eyepiece
attached to the telescope. When using a camera, however, you should always wear corrective lenses to ensure the
sharpest possible focus. If you have astigmatism, corrective lenses must be worn at all times.
ASTRONOMY BASICS
Up to this point, this manual covered the assembly and basic operation of your telescope. However, to understand your
telescope more thoroughly, you need to know a little about the night sky. This section deals with observational astronomy
in general and includes information on the night sky.
With your altazimuth mount, you can use a method called “star hopping” which is described in the
“Celestial Observing Section” later in this manual. Good star maps are essential in helping you locate deep sky objects
and current monthly astronomy magazines will help you locate where the planets are.

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CELESTIAL OBSERVING
Now that your telescope is set up, you’re ready to observe. This section covers visual observing hints for both solar system
and deep sky objects as well as general observing conditions which will affect your ability to observe.
OBSERVING THE MOON
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Often, it is tempting to look at the Moon when it is full. At this time, the face
we see is fully illuminated and its light can be overpowering. In addition, little
or no contrast can be seen during this phase.
One of the best times to observe the Moon is during its partial phases
(around the time of first or third quarter). Long shadows reveal a great
amount of detail on the lunar surface. At low power, you will be able to see
most of the lunar disk at one time. Change to optional eyepieces for higher
power (magnification) to focus in on a smaller area.
Lunar Observing Hints
To increase contrast and bring out detail on the lunar surface, use optional filters. A yellow filter works well at improving
contrast while a neutral density or polarizing filter will reduce overall surface brightness and glare.
OBSERVING THE PLANETS
Other fascinating targets include the five naked-eye planets. You can see
Venus go through its lunar-like phases. Mars can reveal a host of surface
detail and one, if not both, of its polar caps. You will be able to see the cloud
belts of Jupiter and the great Red Spot (if it is visible at the time you are
observing). In addition, you will also be able to see the moons of Jupiter as
they orbit the giant planet. Saturn, with its beautiful rings, is easily visible at
moderate power.
Planetary Observing Hints
• Remember that atmospheric conditions are usually the limiting factor on
how much planetary detail will be visible. So, avoid observing the planets when they are low on the horizon or when they
are directly over a source of radiating heat, such as a rooftop or chimney. See the “Seeing Conditions” section later in
this section.
• To increase contrast and bring out detail on the planetary surface, try using Celestron eyepiece filters.
OBSERVING THE SUN
Although overlooked by many amateur astronomers, solar observation is both rewarding and fun. However, because
the Sun is so bright, special precautions must be taken when observing our star so as not to damage your eyes or your
telescope.
For safe solar viewing, use a proper solar filter that reduces the intensity of the Sun’s light, making it safe to view. With a
filter, you can see sunspots as they move across the solar disk and faculae, which are bright patches seen near the Sun’s
edge.
• The best time to observe the Sun is in the early morning or late afternoon when the air is cooler.
• To center the Sun without looking into the eyepiece, watch the shadow of the telescope tube until it
forms a circular shadow.
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OBSERVING DEEP-SKY OBJECTS
Deep-sky objects are simply those objects outside the boundaries of our solar system. They include star clusters,
planetary nebulae, diffuse nebulae, double stars and other galaxies outside our own Milky Way. Most deep-sky objects
have a large angular size. Therefore, low-to-moderate power is all you need to see them. Visually, they are too faint to
reveal any of the color seen in long exposure photographs. Instead, they appear black and white. And, because of their
low surface brightness, they should be observed from a dark-sky location. Light pollution around large urban areas washes
out most nebulae making them difficult, if not impossible, to observe. Light Pollution Reduction filters help reduce the
background sky brightness, thus increasing contrast.
STAR HOPPING
One convenient way to find deep-sky objects is by star hopping. This technique uses bright stars to “guide” you to an
object. For successful star hopping, it is helpful to know the field of view of your telescope. If you’re using the standard
20 mm eyepiece with the AstroMaster telescope, your field of view is approximately 1º. If you know an object is 3º away
from your present location, then you just need to move 3 fields of view. If you’re using another eyepiece, consult the
section on determining field of view. Below, you’ll find instructions for locating two popular objects.
The Andromeda Galaxy (Figure 4-1), also known as M31, is an easy target.
To find M31:
1. Locate the constellation of Pegasus, a large square visible in the fall (in the eastern sky, moving toward the point
overhead) and winter months (overhead, moving toward the west).
2. Start at the star in the northeast corner—Alpha (α) Andromedae.
3. Move northeast approximately 7°. There you will find two stars of equal brightness—Delta (δ) and Pi (π)
Andromeda—about 3° apart.
4. Continue in the same direction another 8°. There you will find two stars—Beta (β) and Mu (µ) Andromedae—also about
3° apart.
5. Move 3° northwest—the same distance between the two stars—to the Andromeda galaxy.
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Fig. 4-1

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Star hopping to the Andromeda Galaxy (M31) is a snap, since you can locate all the stars needed with the naked eye.
Star hopping will take some getting used to. Objects that don’t have stars near them that are visible to the naked eye are
challenging. One such object is M57 (Figure 4-2), the famed Ring Nebula. Here’s how to find it:
1. Find the constellation of Lyra, a small parallelogram visible in the summer and fall months. Lyra is easy to pick out
because it contains the bright star Vega.
2. Start at the star Vega—Alpha (α) Lyrae—and move a few degrees southeast to find the parallelogram. The four stars that
make up this geometric shape are all similar in brightness, making them easy to see.
3. Locate the two southernmost stars that make up the parallelogram—Beta (β) and Gamma (γ) Lyra.
4. Point about halfway between these two stars.
5. Move about ½° toward Beta (β) Lyra, while remaining on a line connecting the two stars.
6. Look through the telescope and the Ring Nebula should be in your field of view. The Ring Nebula’s angular size is quite
small and difficult to see.
7. Because the Ring Nebula is rather faint, you may need to use “averted vision” to see it. “Averted vision” is a technique
of looking slightly away from the object you’re observing. So, if you are observing the Ring Nebula, center it in your
field of view and then look off toward the side. This causes light from the object viewed to fall on the black and white
sensitive rods of your eyes, rather than your eyes color sensitive cones. (Remember that when observing faint objects,
it’s important to try to observe from a dark location, away from street and city lights. The average eye takes about 20
minutes to fully adapt to the darkness. So always use a red-filtered flashlight to preserve your dark-adapted night vision).
These two examples should give you an idea of how to star hop to deep-sky objects. To use this method on
other objects, consult a star atlas, then star hop to the object of your choice using “naked eye” stars.
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Fig. 4-2

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SEEING CONDITIONS
Viewing conditions affect what you can see through your telescope during an observing session. Conditions include
transparency, sky illumination, and seeing. Understanding viewing conditions and the effect they have on observing will
help you get the most out of your telescope.
Transparency
Transparency is the clarity of the atmosphere which is affected by clouds, moisture, and other airborne particles. Thick
cumulus clouds are completely opaque while cirrus can be thin, allowing the light from the brightest stars through. Hazy
skies absorb more light than clear skies making fainter objects harder to see and reducing contrast on brighter objects.
Aerosols ejected into the upper atmosphere from volcanic eruptions also affect transparency. Ideal conditions are when
the night sky is inky black.
Sky Illumination
General sky brightening caused by the Moon, aurora, natural airglow, and light pollution greatly affect transparency.
While not a problem for the brighter stars and planets, bright skies reduce the contrast of extended nebulae making them
difficult, if not impossible to see. To maximize your observing, limit deep sky viewing to moonless nights far from the light
polluted skies found around major urban areas. LPR filters enhance deep sky viewing from light polluted areas by blocking
unwanted light while transmitting light from certain deep sky objects. You can, on the other hand, observe planets and
stars from light polluted areas or when the Moon is out.
Seeing
Seeing conditions refers to the stability of the atmosphere and directly affects the amount of fine detail seen in extended
objects. The air in our atmosphere acts as a lens which bends and distorts incoming light rays. The amount of bending
depends on air density. Varying temperature layers have different densities and, therefore, bend light differently. Light rays
from the same object arrive slightly displaced creating an imperfect or smeared image. These atmospheric disturbances
vary from time-to-time and place-to-place. The size of the air parcels compared to your aperture determines the “seeing”
quality. Under good seeing conditions, fine detail is visible on the brighter planets like Jupiter and Mars, and stars are
pinpoint images. Under poor seeing conditions, images are blurred and stars appear as blobs.
The conditions described here apply to both visual and photographic observations.
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Fig. 4-3
Seeing conditions directly affect image quality. These drawings represent a point source (i.e., star) under bad seeing
conditions (left) to excellent conditions (right). Most often, seeing conditions produce images that lie somewhere between
these two extremes.

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ASTROPHOTOGRAPHY
The AstroMaster series of telescopes was designed for visual observing. After looking at the night sky for a while you
may want to try your hand at astrophotography. There are several forms of photography possible with your telescope for
celestial as well as terrestrial pursuits. Below is a very brief discussion of some of the methods of photography available.
At a minimum you will need a digital camera or a 35 mm / DSLR camera. Attach your camera to the telescope with:
• Digital camera – you will need the Universal Digital Camera Adapter (# 93626). The adapter allows the camera to be
mounted rigidly for terrestrial as well as prime focus astrophotography.
• 35 mm or DSLR camera – you will need to remove your lens from the camera and attach a T-Ring for your specific
camera brand. Then, you will need a T-Adapter (# 93625) to attach on one end to the T-Ring and the other end to the
telescope focus tube. Your telescope is now the camera lens.
PLANETARY & LUNAR PHOTOGRAPHY WITH SPECIAL IMAGERS
In recent years, a new technology for capturing superb images of the Moon and planets has emerged: dedicated
planetary imagers.
TERRESTRIAL PHOTOGRAPHY
Your telescope makes an excellent telephoto lens for terrestrial (land) photography. You can take images of various
scenic views, wildlife, nature, and just about anything. Try experimenting with focusing, speeds, etc. to get the best image
desired. You can adapt your camera per the instructions at the top of this page.

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TELESCOPE MAINTENANCE
While your telescope requires little maintenance, there are a few things to remember that will ensure your telescope
performs at its best.
CARE AND CLEANING OF THE OPTICS
Occasionally, dust and/or moisture may build up on the objective lens or primary mirror depending on which type of
telescope you have. Special care should be taken when cleaning any instrument so as not to damage the optics.
If dust has built up on the optics, remove it with a brush (made of camel’s hair) or a can of pressurized air. Spray at an
angle to the glass surface for approximately two to four seconds. Then, use an optical cleaning solution and white tissue
paper to remove any remaining debris. Apply the solution to the tissue and then apply the tissue paper to the optics. Low
pressure strokes should go from the center of the lens (or mirror) to the outer portion. Do NOT rub in circles!
You can use a commercially made lens cleaner or mix your own. A good cleaning solution is isopropyl alcohol mixed with
distilled water. The solution should be 60% isopropyl alcohol and 40% distilled water. Or, liquid dish soap diluted with
water (a couple of drops per one quart of water) can be used.
Occasionally, you may experience dew build-up on the optics of your telescope during an observing session. If you want
to continue observing, the dew must be removed, either with a hair dryer (on low setting) or by pointing the telescope at
the ground until the dew has evaporated.
If moisture condenses on the inside of the optics, remove the accessories from the telescope. Place the telescope in a
dust-free environment and point it down. This will remove the moisture from the telescope tube.
To minimize the need to clean your telescope, replace all lens covers once you have finished observing. Since the cells are
NOT sealed, the covers should be placed over the openings when not in use. This will prevent contaminants from entering
the optical tube.
Internal adjustments and cleaning should be done only by the Celestron repair department. If your telescope is in need of
internal cleaning, please call the factory for a return authorization number and price quote.

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OPTIONAL ACCESSORIES
You will find that additional accessories for your AstroMaster telescope will enhance your enjoyment and the usefulness
of your telescope. This is just a short list of various accessories with a brief description. Visit the Celestron website for
complete descriptions of all accessories available.
Sky Maps (# 93722) – Celestron Sky Maps are the ideal teaching guide for learning the night sky.
Even if you already know your way around the major constellations, these maps can help you locate
all kinds of fascinating objects.
Omni Plossl Eyepieces – These eyepieces are affordable and offer razor sharp views across the entire
field. They are a 4-element lens design and have the following focal lengths: 4 mm, 6 mm, 9 mm, 12.5
mm, 15 mm, 20 mm, 25 mm,
32 mm, and 40 mm – all in 1.25” barrels.
Omni Barlow Lens ( #93326)– A Barlow lens doubles the magnification of any eyepiece with which it is paired. The 2x
Omni is a 1.25” barrel, is under 3 inches (76mm) long, and weights only 4 oz (113 g).
Moon Filter (# 94119-A) – This is an economical 1.25” eyepiece filter for reducing the brightness of the moon and
improving contrast, so you can observe greater detail on the lunar surface.
UHC/LPR Filter 1.25” (# 94123) – This filter is designed to enhance your views of deep sky
astronomical objects when viewed from urban areas. It selectively reduces the transmission of certain
wavelengths of light, specifically those produced by artificial lights.
Night Vision Flashlight (# 93588) – The Celestron flashlight uses two red LED’s to preserve night vision better than
red filters or other devices. Brightness is adjustable. Operates on a single 9-volt included battery.
Digital Camera Adapter – Universal # 93626) – A universal mounting platform that allows you to do
afocal photography (photography through the eyepiece of a telescope) using 1.25” eyepieces with your
digital camera.
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AstroMaster Specications 22065
AstroMaster 102 AZ
Optical Design Refractor
Aperture 102 mm (4.0”)
Focal Length 660 mm
Focal Ratio f/6.5
Optical Coatings Fully Coated
Finderscope Red Dot Finder
Diagonal 1.25” Erect Image
Eyepieces 1.25” 20 mm (33x)
Apparent FOV -- 20mm @ 50°
-- 10mm @ 40° 10 mm (66x)
Angular Field of View w/standard eyepiece 1.5°
Linear FOV w/standard eyepiece -ft/1000yds 78.5
Mount Altazimuth
Pan Handle Control for Altitude yes
Azimuth Lock yes
Tripod Leg Diameter 1.25” yes
TheSkyX-First Light Edition software yes
Highest Useful Magnification 240x
Limiting Stellar Magnitude 1.37
Resolution -- Raleigh (arc seconds) 1.14
Resolution -- Dawes Limit “ “ 1.29
Light Gathering Power 212x
Optical Tube Length 36” (91cm)
Telescope Weight 20 # (9kg)
Note: Specifications are subject to change without notice or obligation.