Getting Started - Orion 9768 Instruction Manual

getting started

The telescope will arrive in one box. We recommend keep-
ing the box and all original packaging. In case the telescope
needs to be shipped to another location, or returned to Orion
for warranty repair, having the proper box and packaging will
help ensure your telescope will survive the journey intact. The
box also makes a good container for storing the telescope
when not in use.
In addition to the optical tube assembly, you will find a collima-
tion cap, rear cover plate, and two cover plate thumbscrews.
Dust covers for the front opening of the tube and for the
focuser drawtube are also included.
installing the rear cover Plate
The rear cover plate reduces the amount of light that can enter
the telescope from behind the mirror cell, which improves
image contrast. It can be removed prior to observing to facili-
tate rapid cooling of the primary mirror, which ensures the
best views through the telescope. To install the rear cover
plate (if not already on the mirror cell), simply line up the small
holes in the cover plate with two of the four threaded holes in
the rear of the mirror cell. Then, thread the cover plate thumb-
screws through the cover plate and into the rear of the mirror
cell (Figure 2). The larger hole in the center of the cover plate
is a finger hole to make it easier to remove the plate.
Figure 2.
Thread the cover plate thumbscrews through the rear
cover plate and into two of the threaded holes in the back of the
mirror cell.
connecting to a Mount
Optional tube rings should be used to attach the scope to a
telescope mount. Tube rings with an inner diameter of 182mm
(7.2"), such as Orion item #7375, are needed.
use of optional Eyepieces and Finder scope
The 3.6" CA reflector does not come with a finder scope or
eyepieces in order to grant the user the greatest versatility in
customizing the instrument to suit their needs.
Any Orion finder scope with a dovetail bracket can be used
with the 3.6" CA reflector. Simply unthread the thumbscrew on
the tube's dovetail mount (Figure 1) and insert the assembled
2
finder scope and dovetail bracket. Then retighten the thumb-
screw. Finder scope brackets that do not match the dovetail
mount will need to be attached by some other means.
The 3.6" CA reflector can use almost any 1.25" eyepiece.
Remove the cover cap from the focuser drawtube, loosen
the two thumbscrews, and insert the eyepiece. Secure the
eyepiece with the thumbscrews on the drawtube. Focus the
telescope by rotating one of the focus knobs.
Magnification & Eyepieces
Magnification, or power, is determined by the focal length of
the telescope and the focal length of the eyepiece. Therefore,
by using eyepieces of different focal lengths, the resultant
magnification can be varied.
Magnification is calculated as follows:
Telescope Focal Length (mm)
Eyepiece Focal Length (mm)
The 3.6" CA reflector has a focal length of 1240mm, so when
used with a 25mm eyepiece yields:
1240 mm
25 mm
The magnification provided by a 10mm eyepiece is:
1240 mm
10 mm
The maximum attainable magnification for a telescope is
directly related to how much light it can gather. The larger the
aperture, the more magnification is possible. In general, a fig-
ure of 50x per inch of aperture is the maximum attainable for
most telescopes. Your 3.6" CA reflector has an aperture of 3.6
inches, so the maximum magnification would be about 180x.
This level of magnification assumes you have ideal conditions
for viewing.
Keep in mind that as you increase magnification, the bright-
ness of the object viewed will decrease; this is an inherent
principle of the laws of physics and cannot be avoided. If
magnification is doubled, an image appears four times dim-
mer. If magnification is tripled, image brightness is reduced
by a factor of nine!
It is quite common for an observer to own five or more eye-
pieces to access a wide range of magnifications. This allows
the observer to choose the best eyepiece to use depending
on the object being viewed.
Whatever you choose to view, always start by inserting your
lowest power (longest focal length) eyepiece to locate and
center the object. Low magnification yields a wide field of
view, which shows a larger area of sky in the eyepiece. This
makes acquiring and centering an object much easier. If you
try to find and center objects with high power (narrow field of
view), it's like trying to find a needle in a haystack!
= Magnification
= 50x
= 124x