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Magnification = Telescope Focal Length (mm)
Eyepiece Focal Length (mm)
For example, the Observer 60 EQ, which has a focal length
of 900mm, used in combination with a 25mm eyepiece, yields
a power of
900 ÷ 25 = 36x.
Every telescope has a useful limit of power of about 45x–60x per
inch of aperture (diameter of objective lens). Claims of higher
power by some telescope manufacturers are a misleading adver-
tising gimmick and should be dismissed. Keep in mind that at
higher powers, an image will always be dimmer and less sharp
(this is a fundamental law of optics). The steadiness of the air (the
“seeing”) will limit how much magnification an image can tolerate.
Always start viewing with your lowest-power (longest focal
length) eyepiece in the telescope. After you’ve located and
looked at the object with it, you can try switching to a higher-
power eyepiece to ferret out more detail, if atmospheric
conditions permit. If the image you see is not crisp and
steady, reduce the magnification by switching to a longer-
focal-length eyepiece. As a general rule, a small but
well-resolved image will show more detail and provide a more
enjoyable view than a dim and fuzzy, overmagnified image.
Camera Attachment
A 35mm single-lens reflex (SLR) camera body can easily be
attached to the Observer 60mm enabling you to take pictures
through the telescope. All that is needed is two additional
parts; a t-ring, which is specific to your model of camera (see
Orion catalog or www.telescope.com for selection), and a
camera adapter (#8782).
Remove the eyepiece and diagonal from the telescope opti-
cal tube. Also remove any lenses that may already be
attached to your camera body. Now, connect the T-ring to
your camera. For prime focus or daytime photography,
remove the nosepiece from the camera adapter and connect
it to the T-ring on the camera. Now, insert the entire assem-
bly into the telescope’s focuser drawtube, and secure with the
setscrews on the drawtube. Tighten the setscrews firmly, or
else you risk having your camera fall to the ground! When
used in this configuration, the Observer 60 EQ acts as a
900mm telephoto lens (the focal length of the telescope).
Let Your Eyes Dark-Adapt
Don’t expect to go from a lighted house into the darkness of
the outdoors at night and immediately see faint nebulas,
galaxies, and star clusters—or even very many stars, for that
matter. Your eyes take about 30 minutes to reach perhaps
80% of their full dark-adapted sensitivity. Many observers
notice improvements after several hours of total darkness. As
your eyes become dark-adapted, more stars will glimmer into
view and you’ll be able to see fainter details in objects you
view in your telescope. Exposing your eyes to very bright
daylight for extended periods of time can adversely affect
your night vision for days. So give yourself at least a little
while to get used to the dark before you begin observing.
To see what you’re doing in the darkness, use a red-filtered
flashlight rather than a white light. Red light does not spoil
your eyes’ dark adaptation like white light does. A flashlight
with a red LED light is ideal, or you can cover the front of a
regular incandescent flashlight with red cellophane or paper.
Beware, too, that nearby porch and street lights and car
headlights will ruin your night vision.
“Seeing” and Transparency
Atmospheric conditions vary significantly from night to night.
“Seeing” refers to the steadiness of the Earth’s atmosphere at
a given time. In conditions of poor seeing, atmospheric turbu-
lence causes objects viewed through the telescope to “boil.” If,
when you look up at the sky with just your eyes, the stars are
twinkling noticeably, the seeing is bad and you will be limited to
viewing with low powers (bad seeing affects images at high
powers more severely). Planetary observing may also be poor.
In conditions of good seeing, star twinkling is minimal and
images appear steady in the eyepiece. Seeing is best over-
head, worst at the horizon. Also, seeing generally gets better
after midnight, when much of the heat absorbed by the Earth
during the day has radiated off into space.
Avoid looking over buildings, pavement, or any other source
of heat, as they will cause “heat wave” disturbances that will
distort the image you see through the telescope.
Especially important for observing faint objects is good
“transparency”—air free of moisture, smoke, and dust. All
tend to scatter light, which reduces an object’s brightness.
Transparency is judged by the magnitude of the faintest
stars you can see with the unaided eye (6th magnitude or
fainter is desirable).
How to Find Interesting Celestial Objects
To locate celestial objects with your telescope, you first need
to become reasonably familiar with the night sky. Unless you
know how to recognize the constellation Orion, for instance,
you won’t have much luck locating the Orion Nebula, unless,
or course, you look up its celestial coordinates and use the
telescope’s setting circles. Even then, it would be good to
know in advance whether that constellation will be above the
horizon at the time you plan to observe. A simple planisphere,
or star wheel, can be a valuable tool both for learning the con-
stellations and for determining which ones are visible on a
given night at a given time.
A good star chart or atlas will come in very handy for helping
find objects among the dizzying multitude of stars overhead.
Except for the Moon and the brighter planets, it’s pretty time-
consuming and frustrating to hunt for objects randomly,
without knowing where to look. You should have specific tar-
gets in mind before you begin observing.
Start with a basic star atlas, one that shows stars no fainter
than 5th or 6th magnitude. In addition to stars, the atlas will
show the positions of a number of interesting deep-sky
objects, with different symbols representing the different
types of objects, such as galaxies, open star clusters, globu-
lar clusters, diffuse nebulas, and planetary nebulas. So, for
example, your atlas might show that there is a globular clus-
