Orion XT12 - Manual (Page 14)

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If you have trouble focusing, rotate the focusing knob so the
drawtube is in as far as it will go. Now look through the eyepiece
while slowly rotating the focusing knob in the opposite direction.
You should soon see the point at which focus is reached.
The thumb screw on the top of the body of the focuser (Figure
20) will lock the focuser drawtube in place once the telescope
is properly focused. Before focusing, remember to first loosen
this thumb screw. Do not loosen the thumb screw too much
as there must be some tension to keep the drawtube secure
within the focuser.
If you find the drawtube tension when focusing is either too
tight (focus knob is difficult to turn) or too loose (image shifts
when focusing), you can adjust it by tightening or loosen-
ing the two drawtube tensioning set screws on the focuser.
These are the two small set screws located on either side
of the focus lock thumb screw. Adjusting these set screws
requires a 1.5mm hex key.
Note About the Focuser Drawtube Lock Knob
The focusers of the SkyQuest XT12 IntelliScope feature a
drawtube lock knob. There are times when you may want to
lock the drawtube to preserve the focus setting (such as when
using certain afocal photographic attachments). This is done
by turning the focus lock knob (Figure 20) clockwise until it is
tight. The focus setting will now be locked. When you need to
adjust the focus again, be sure to loosen the lock knob.
Viewing with Eyeglasses
If you wear eyeglasses, you may be able to keep them on
while you observe, if your eyepieces have enough eye relief
to allow you to see the whole field of view. You can try this by
looking through the eyepiece first with your glasses on and
then with them off, and see if the glasses restrict the view
to only a portion of the full field. If they do, you can easily
observe with your glasses off by just refocusing the telescope
the needed amount. If you suffer from severe astigmatism,
however, you may find images noticeably sharper with your
glasses on.
Aligning the Finder Scope
The finder scope must be aligned accurately with the tele-
scope for proper use. To align it, first aim the main telescope
in the general direction of an object at least 1/4-mile away
- the top of a telephone pole, a chimney, etc. Position that
object in the center of the telescope’s eyepiece.
The finder scope uses a spring-loaded bracket that makes
alignment of the finderscope very easy. As you turn either of
the thumbscrews, the spring in the bracket’s tensioner moves
in and out to keep the finder scope secure in the bracket.
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 30).
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 align-
ment thumbscrews to center the object on the intersection 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.
Focusing the Finder Scope
The finder scope with your SkyQuest XT12 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 19a).
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.
Naked-eye view
Figure 30. The view through a standard finder scope and reflec-
tor telescope is upside down. This is true for the SkyQuest XT12
Intelliscope and its finder scope as well.
View through finder scope and telescope