Orion SHORTTUBE 80-A User Manual download pdf (Page 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

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

instrument without a professionally made solar filter, or per-

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

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Orion SHORTTUBE 80-A User Manual Page 5

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