10
Note: The image in both the finder scope and the main
telescope will appear upside-down (rotated 180°). This is
normal for finder scopes and reflector telescopes (see
Figure 16).
Now look through the finder scope. Ideally, the object should
be within the field of view. If not then coarse adjustments to
the alignment thumbscrews will be needed. Once the image
is in the finder scope’s field of view, you will now use the
alignment thumbscrews to center the object on the intersec-
tion of the crosshairs. By loosening one alignment
thumbscrew, you change the line of sight of the finder scope.
Continue making adjustments to the alignment thumbscrews
until the image in both the finder scope and the telescope’s
eyepiece is exactly centered.
Check the alignment by moving the telescope to another
object and fixing the finder scope’s crosshairs on the exact
point you want to look at. Then look through the telescope’s
eyepiece to see if that point is centered in the field of view. If it
is, the job is done. If not, make the necessary adjustments
until the two images match up.
The finder scope alignment should be checked before every
observing session. This can easily be done at night, before
viewing through the telescope. Choose any bright star or
planet, center the object in the telescope eyepiece, and then
adjust the finder scope’s alignment thumb screws until the
star or planet is also centered on the finder’s crosshairs. The
finder scope is an invaluable tool for locating objects in the
night sky; its usage for this purpose will be discussed later.
Focusing the Finder Scope
The finder scope with your SkyQuest IntelliScope has
adjustable focus. If the images in the finder appear somewhat
out of focus, you will need to refocus the finder scope for your
vision. Loosen the lock ring located behind the objective lens
cell on the body of the finder scope (see Figure 12a). Back
the lock ring off by a few turns, for now. Focus the finder
scope on a distant object by threading the objective lens cell
in or out on 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 finder scope’s focus should not need
to be adjusted again.
Aiming/Pointing the Telescope
With the finder scope aligned, the telescope can be quickly
and accurately pointed at anything you wish to observe. The
finder scope has a much wider field of view than the tele-
scope’s eyepiece, and therefore it is much easier to find and
center an object in the finder scope. Then, if the finder scope
is accurately aligned, the object will also be centered in the
telescope’s field of view.
Start by once again moving the telescope until it is pointed in
the general direction of the object you want to see. Some
observers find it convenient to sight along the tube to do this.
Now, look in the finder scope. If your general aim is accurate,
the object should appear somewhere in the field of view.
Make small adjustments to the telescope’s position until the
object is centered on the finder’s crosshairs. Now, look in the
telescope’s eyepiece and enjoy the view!
Some objects are too faint to be seen with the small aperture
of the finder scope. In those cases, you will need to interpo-
late your position using stars as guideposts. A star map will
help you in doing so.
Magnification
Now that the object you want to view is centered in the 25mm
eyepiece, you may want to increase the magnification to get a
closer view. Loosen the thumbscrew(s) on the focuser draw-
tube and remove the eyepiece. Place it in the eyepiece rack,
if you wish. Insert the 10mm eyepiece in the focuser then
tighten the thumbscrew(s). If you were careful not to bump the
telescope, the object should still be visible in the field of view.
Notice that the object being viewed is now larger, but some-
what dimmer.
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)
Magnification=
Eyepiece Focal Length (mm)
All three SkyQuest IntelliScope Dobsonian models have a
focal length of 1200mm. So, the magnification with the sup-
plied 25mm eyepiece is:
1200 mm
= 48x
25 mm
The magnification provided by the 10mm eyepiece is:
Naked-eye view
Figure 16.
The view through a standard finder scope and
reflector telescope is upside down. This is true for the SkyQuest
Intelliscope and its finder scope as well.
View through finder scope and telescope
