Orion SKYWATCHER 9086 - Manual (Page 5)

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rotate freely about the R.A. axis. Rotate it until the coun-
terweight shaft is parallel to the ground (i.e., horizontal).
2. Now loosen the counterweight locking thumbscrew and
slide the weight along the shaft until it exactly counterbal-
ances the telescope. (Figure 2a) That’s the point at which
the shaft remains horizontal even when you let go with
both hands (Figure 2b).
3. Retighten the counterweight locking thumbscrew. The tel-
escope is now balanced on the R.A. axis.
4. To balance the telescope on the Dec. axis, first tighten the
R.A. lock knob, with the counterweight shaft still in the hor-
izontal position.
5. With one hand on the telescope optical tube, loosen the
Dec. lock knob (Figure 2c). The telescope should now be
able to rotate freely about the Dec. axis. Loosen the tube
ring clamps a few turns, until you can slide the telescope
tube forward and back inside the rings (this can be aided
by using a slight twisting motion on the optical tube while
you push or pull on it) (Figure 2d).
6. Position the telescope in the mounting rings so it remains
horizontal when you carefully let go with both hands. This
is the balance point for the optical tube with respect to the
Dec. axis (Figure 2e).
7. Retighten the tube ring clamps.
The telescope is now balanced on both axes. Now when you
loosen the lock knob on one or both axes and manually point
the telescope, it should move without resistance and should
not drift from where you point it.
4. Aligning the Finder Scope
A finder scope has a wide field of view to facilitate the loca-
tion of objects for subsequent viewing through the main
telescope, which has a much narrower field of view. The find-
er scope and the main telescope must be aligned so they
point to exactly the same spot in the sky.
Alignment is easiest to do in daylight hours. First, insert the
lowest-power (25mm) eyepiece into the star diagonal. Then
loosen the R.A. and Dec. lock knobs so the telescope can be
moved freely.
Point the main 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 eye-
piece. Now tighten the R.A. and Dec. lock knobs. Use the
slow-motion control knobs to re-center the object in the field of
view, if it moved off-center when you tightened the lock knobs.
Now look through the finder scope. Is the object centered in
the finder scope’s field of view, (i.e., at the intersection of the
crosshairs)? If not, hopefully it will be visible somewhere in
the field of view, so that only fine adjustment of the finder
scope alignment screws will be needed to center it on the
crosshairs. Otherwise you’ll have to make coarser adjust-
ments to the alignment screws to redirect the aim of the finder
scope. Make sure the knurled lock nut on each alignment
screw is loosened before making any adjustments.
Once the target object is centered on the crosshairs of the
finder scope, look again in 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.
When the target object is centered on the crosshairs of the
finder scope and in the telescope’s eyepiece, tighten the
knurled lock nuts on the alignment screws to lock the finder
scope into position. The finder scope is now aligned and ready
to be used for an observing session. The finder scope and
bracket can be removed from the dovetail for storage, and then
re-installed without changing the finder scope’s alignment.
Note that the image seen through the finder scope appears
upside down. This is normal for astronomical finder scopes.
5. Setting Up and Using
the Equatorial Mount
When you look at the night sky, you no doubt have noticed
that the stars appear to move slowly from east to west over
time. That apparent motion is caused by the Earth’s rotation
(from west to east). An equatorial mount (Figure 3) is
designed to compensate for that motion, allowing you to eas-
ily “track” the movement of astronomical objects, thereby
keeping them from drifting out of the telescope’s field of view
while you’re observing.
This is accomplished by slowly rotating the telescope on its
right ascension (polar) axis, using only the R.A. slow-motion
cable. But first the R.A. axis of the mount must be aligned with
the Earth’s rotational (polar) axis—a process called polar
alignment.
Polar Alignment
For Northern Hemisphere observers, approximate polar
alignment is achieved by pointing the mount’s R.A. axis at the
North Star, or Polaris. It lies within 1 degree of the north
celestial pole (NCP), which is an extension of the Earth’s rota-
tional axis out into space. Stars in the Northern Hemisphere
appear to revolve around Polaris.
To find Polaris in the sky, look north and locate the pattern of
the Big Dipper (Figure 4). The two stars at the end of the
“bowl” of the Big Dipper point right to Polaris.
Observers in the Southern Hemisphere aren’t so fortunate to
have a bright star so near the south celestial pole (SCP). The
star Sigma Octantis lies about 1 degree from the SCP, but it
is barely visible with the naked eye (magnitude 5.5).
For general visual observation, an approximate polar align-
ment is sufficient:
1. Level the equatorial mount by adjusting the length of the
three tripod legs.
2. Loosen the latitude locking t-bolt. Turn the latitude adjust-
ing t-bolt and tilt the mount until the pointer on the latitude