Orion ShortTube User Manual

IN 114 Rev. C 0899

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INSTRUCTION MANUAL

Orion

®

ShortTube

™

90

90mm Rich-Field Refracting Telescope

#9069

W

elcome to a new world of adventure!

Your Orion ShortTube 90 is a fine-quality instrument designed for both daytime ter­restrial viewing and nighttime stargazing. Compact, por table, and easy to use, this versatile scope will provide many hours of
enjoyment for the whole family.

These instructions will help you set up and properly use and care for your telescope. Please read them over
thoroughly before getting started.

Parts List

Qty. Description
1 Optical tube assembly
1 26mm (19x) Plössl eyepiece (1.25")
1 90° star diagonal
1 6x30 finder scope
1 Objective lens cap

Getting Started

The ShortTube 90 comes nearly fully assembled from the factory.The
telescope’s optics have been installed and collimated, so you should
not have to make any adjustments to them.Open the box and inspect
the contents to make sure all of the parts listed above are present.

WARNING:

Never look at the sun with your telescope
(or even with just your eyes) without a professionally made
solar filter.Permanent eye damage or blindness could
result.Young children should use this telescope only with
adult supervision.

Avoid using the type of solar filter that screws into an eye­piece. They are susceptible to cracking under the intense
heat that builds up near the focus point, and could cause
severe retinal damage. Use only the type of solar filter that
covers the front of the telescope. Be sure also to cover the
front of the finder scope with aluminum foil or another
opaque material to prevent physical damage to the internal
components of the scope itself as well as to your eyes.

Finder scope bracket

1/4"-20 mounting block

Dew/glare shield

Finder scope

Finder scope alignment screws

Focus lock setscrew

Eyepiece

Focus wheel

90° star diagonal

The ShortTube 90mm Refractor

2

Please keep the original shipping box! In the unlikely event you
should need to ship the telescope back to Orion for warranty repair
service, you should use the original packaging.The box also makes
a very good container for storing the telescope when it is not in use.

Installing the Accessories

Slide the 6x30 finder scope into its mounting bracket (preinstalled on
the optical tube) and gently tighten the six alignment screws.Insert the
90° star diagonal into the focuser drawtube and secure with the
knurled setscrew.Slide the eyepiece into the diagonal and tighten the
setscrew on the diagonal.

Mounting the Telescope on a Tripod

The ShortTube 90 can be mounted on an y standard camera tripod that
has a 1/4"-20 stud.The stud threads into the small block on the under­side of the telescope’s optical tube.Alternatively, the telescope can be
attached to an equatorial mount equipped with a 1/4"-20 adapter. An
equatorial mount is desirable for astronomical viewing because it
allows easy manual tracking of celestial objects as the Earth rotates.
Also, the setting circles on the mount enable you to locate objects by
their celestial coordinates (right ascension and declination), which can
be found in many observing books and star atlases.

Focusing

The ShortTube 90 is equipped with a precision rack-and-pinion
focuser.When you first look in the eyepiece, the image you see may
be fuzzy, or out of focus. If so, gently turn one of the large focusing
wheels with your fingers until the image becomes sharp. Be sure to
first loosen the knurled focus lock setscrew on the top of the focuser.
You will have to readjust the focus when aiming at subjects of vary­ing distances, or after changing eyepieces.

Aligning the Finder Scope

The ShortTube 90 comes with a 6x30 achromatic finder scope .(The 6
means six-times magnification, and the 30 indicates a 30mm-diame­ter front lens.) The finder scope makes it easier to locate the subject
you want to observe in the telescope, because the finder scope has a
much wider field of view .Images viewed in the finder scope will appear
upside down, which is normal for astronomical finder scopes.

Before you can properly use the finder scope, it must be precisely
aligned with the telescope, so they both point to exactly the same spot.
Alignment is easiest to do in daylight, rather than at night under the
stars.First, insert the eyepiece into the main telescope’s focuser.Then
point the telescope at a discrete object such as the top of a telephone
pole or a street sign that is at least a quarter-mile away.Move the tele­scope so the target object appears in the very center of the field of view
when you look into the eyepiece.

Now look through the finder scope.Is the object centered in the find­er scope’s field of view, i.e., on the crosshairs? If not, hopefully it will
be visible somewhere in the field of view, so only fine adjustment of
the six alignment screws will be needed. Otherwise you’ll have to
make coarser adjustments to the alignment screws to redirect the
aim of the finder scope. Make sure to loosen the knurled lock nut on
each alignment screw before adjusting it.

Use the six 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 observing session.Note
that the image seen through the finder scope appears upside-down.
This is normal for astronomical finder scopes.

Terrestrial Viewing

For terrestrial observing, you may wish to replace the standard­equipment 90° star diagonal with an optional 45° correct-image
diagonal (Orion part #8790). The 90° star diagonal is preferred for
astronomical use, but gives an image that is reversed left-to-right,
which doesn’t really matter when viewing celestial objects. For day­time terrestrial use, however, you will want a properly oriented image,
so use of the 45° correct-image diagonal is recommended.

For terrestrial applications, we recommend mounting the ShortTube
90 on an altazimuth-style camera tripod (such as the Orion Paragon
HD-F2) or telescope mount (Orion AZ-3 mount), which allow simple
vertical (altitude) and horizontal (azimuth) motions. For most astro­nomical telescope mounts, you will need a 1/4"-20 adapter to couple
the scope to the mount head.Camera tripods come already equipped
with a 1/4"-20 post, so no adapter is needed.

With the eyepiece inserted and secured in the diagonal, simply point
the telescope at the subject you want to observe and center it on
crosshairs of the finder scope (which you’ve previously aligned with
the telescope, as explained in the preceding section).Then look into
the eyepiece of the main telescope and the subject should be in the
center of the field of view. If the view is blurry, adjust the focus with
the focus wheel until the image appears sharp.

For higher magnification, additional eyepieces of shorter focal length
can be purchased. But remember, increasing the magnification
decreases the field of view and the image brightness.

Astronomical Viewing

The ShortTube 90 excels for astronomical observation. Its unob­structed 90mm aperture and short 500mm focal length (f/5.6) provide
bright, expansive views of star fields and celestial objects residing
within our solar system and beyond.

For casual stargazing, an altazimuth mount such as the Orion AZ-3
mount will do the job just fine. But an equator ial mount, such as the
Orion SkyView Deluxe EQ mount, is designed to make it easier to man­ually “track” the motion of celestial objects with just one slow-motion
cable. Furthermore, with an equatorial mount you can add an optional
motor drive to track the stars automatically — 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, such as the Orion
RedBeam LED 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 visible in the sky on a given night.

A good star chart or atlas, like the Orion DeepMap 600, 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 looking 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 mountain formations offer endless fascina­tion.The best time to observe the Moon is during a partial phase, that