5
Use the two alignment screws to center the object on the
crosshairs of the finder scope. Then look again into the main
telescope’s eyepiece and see if it is still centered there as
well. If it isn’t, repeat the entire process, making sure not to
move the main telescope while adjusting the alignment of
the finder scope.
Finder scopes can come out of alignment during transport of
the telescope, so check the alignment before each observ-
ing session.
Focusing the Finder Scope
If, when looking through the finder scope, you notice that
the images appear somewhat out of focus, you will need to
refocus the finder scope for your eyes. First loosen the lock
ring located behind the objective lens cell on the body of the
finder scope (see Figure 2a). Back the lock ring off by a few
turns, for now. Refocus the finder scope on a distant object
by threading the objective lens cell in or out of the finder
scope body. Precise focusing will be achieved by focusing the
finder scope on a bright star. Once the image appears sharp,
retighten the lock ring behind the objective lens cell. The find-
er scope’s focus should not need to be adjusted again.
Astronomical Viewing
The ShortTube 80-A excels for astronomical observation. Its
unobstructed 80mm aperture and short 400mm focal length
(f/5) provide bright, expansive views of star fields and celes-
tial objects residing within our solar system and beyond.
Once the Sun sets, there are literally thousands of objects in
the night sky that can be inspected more closely. For astro-
nomical usage, we’ve included a 90° mirror star diagonal.
The viewing angle provided by a star diagonal is comfortable
for looking up. Keep in mind when using a star diagonal, the
image in the eyepiece will appear backwards (inverted left-
to-right).
For casual stargazing, an altazimuth mount mount will do
the job just fine. But an equatorial mount is designed to
make it easier to manually “track” the motion of celestial
objects (due to the rotation of the Earth) with just one slow-
motion cable. Furthermore, with an equatorial mount you
can add an optional motor drive to track the stars automati-
cally—a great convenience.
When selecting a location for nighttime stargazing, make
it as far away from city lights as possible. Light-polluted
skies greatly reduce what can be seen with the telescope.
Also, give your eyes at least 20 minutes to dark-adapt to the
night sky. You’ll be surprised at how many more stars you
will see! Use a red flashlight to see what you’re doing at the
telescope, or to read star charts. Red light will not spoil your
dark-adapted night vision as readily as white light will.
To find 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. A
simple planisphere, or star wheel, can be a valuable tool for
learning the constellations and seeing which ones are vis-
ible in the sky on a given night.
A good star chart or atlas can come in handy for helping
A good star chart or atlas can come in handy for helping
locate interesting objects among the dizzying multitude
of stars overhead. Except for the Moon and the brighter
planets, it is pretty time-consuming and frustrating to hunt
for objects randomly, without knowing where to look. It is
best to have specific targets in mind before you begin look-
ing through the eyepiece.
A. The Moon
The Moon, with its rocky, cratered surface, is one of the
easiest and most interesting subjects to observe with your
telescope. The myriad craters, rilles, and jagged moun-
tain formations offer endless fascination. The best time to
observe the Moon is during a partial phase, that is, when
the Moon is not full. During partial phases, shadows cast by
crater walls and mountain peaks along the border between
the dark and light portions of the lunar disk highlight the
surface relief. A full Moon is too bright and devoid of surface
shadows to yield a pleasing view. Try using a Moon filter to
dim the Moon when it is too bright; it simply threads onto the
bottom of the eyepiece.
B. The Sun
You can change your nighttime telescope into a daytime Sun
viewer by installing an optional full-aperture solar filter over
the front opening of the ShortTube 80-A. The primary attrac-
tion is sunspots, which change shape, appearance, and loca-
tion daily. Sunspots are directly related to magnetic activity in
the Sun. Many observers like to make drawings of sunspots
to monitor how the Sun is changing from day to day.
Important Note: Do not look at the Sun with any optical
Important Note: Do not look at the Sun with any optical
instrument without a professionally made solar filter, or per-
instrument without a professionally made solar filter, or per-
manent eye damage could result. Also, remember to cover
manent eye damage could result. Also, remember to cover
or remove the finder scope.
C. The Planets
The planets don’t stay put like stars do (planets don’t have
fixed R.A. and Dec. coordinates), so you will have to refer to
Sky Calendar at our website, www.OrionTelescope.com, or
to charts published monthly in
Astronomy
,
Astronomy
Astronomy Sky & Telescope
,
or other astronomy references to locate them. Venus, Mars,
Jupiter, and Saturn are the brightest objects in the sky after
the Sun and the Moon. All four of these planets are not nor-
mally visible in the sky at one time, but chances are one or
two of them will be.
D. Stars
Stars will appear like twinkling points of light in the tele-
scope. Even the largest telescopes cannot magnify stars
to appear as anything more than points of light! You can,
however, enjoy the different colors of the stars and locate
many pretty double and multiple stars. The famous “Double-
Double” in the constellation Lyra and the gorgeous two-color
double star Albireo in Cygnus are favorites. Defocusing the
image of a star slightly can help bring out its color.
E. Deep-Sky Objects
Under dark skies, you can observe a number of brighter
deep-sky objects with your ShortTube 80-A, including gas-
eous nebulas, open and globular star clusters, and the
brighter galaxies. Most deep-sky objects are very faint, so it
