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Therefore, if you use the 20mm eyepiece your magnification is 700/20 = 35x. The same formula can be applied to
any of your eyepieces.
Celestron offers numerous optional eyepieces to expand your range of magnification. Eyepieces come in barrel
diameters of .96" and 1¼". In general, 1¼" eyepieces are of a higher optical quality and give you sharper images,
along with a wider field of view and better eye relief.
Magnification through the telescope has its limits. These limits are determined by the laws of optics and the nature
of the human eye. The maximum usable power (with sharp images) is equal to 60 times the aperture of the telescope
(in inches). So, with a 60mm telescope it has a maximum useful power of 144x (2.4" x 60) and with the 70mm the
maximum is 165x (2.7559 x 60). Most of your viewing will be done in the range of 30x to 120x. Higher powers are
used mainly for lunar and sometimes planetary observing where you can greatly enlarge the image. The images at
extremely high powers like 675x magnify the image bur remember that the contrast will be very low and the image
somewhat blurred due to the super power. For the brightest images with the most contrast, use the lower powers
with a smaller image scale.
T
T
E
E
L
L
E
E
S
S
C
C
O
O
P
P
E
E
O
O
P
P
E
E
R
R
A
A
T
T
I
I
O
O
N
N
—
—
A
A
S
S
T
T
R
R
O
O
N
N
O
O
M
M
I
I
C
C
A
A
L
L
O
O
B
B
S
S
E
E
R
R
V
V
I
I
N
N
G
G
Now that your telescope is set up, you’re ready to use it for observing.
Observing the Moon
In the night sky, the moon is a prime target for your first look because it
is extremely bright and easy to find. Although the beauty of the full
moon may make it seem a perfect viewing object, in fact, the light
reflected from its fully illuminated face 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,
such as a crescent or quarter moon. At these times, long shadows reveal a
great amount of detail on the lunar surface. At low power, with the
standard eyepiece, you’ll be able to see the whole lunar disk at one time.
Change to higher power (magnification) to focus in on a smaller area.
Keep in mind that the rotation of the earth will cause the moon to drift out of your field of view. You’ll have to
manually adjust the telescope to keep the moon centered. This effect is more noticeable at higher power. Consult a
current astronomy magazine or your local newspaper to find out the current phase of the moon.
Lunar Observing Hint
To increase contrast and bring out visible detail on the lunar surface, try using different eyepiece filters (available
through your local Celestron dealer). A yellow filter works well for improving contrast.
Observing the Planets
Other easy targets include the five “naked eye” planets of our solar system, so called because they can be spotted in
the night sky by the unaided eye. 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’ll be able to see the cloud belts of Jupiter, perhaps even
the great Red Spot. In addition, you’ll 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, as is Mercury. All you need to know is where to look.
Most astronomy publications indicate where the planets are in the sky each month.