7
2. Now loosen the counterweight lock bolt and slide the weight
along the shaft until it exactly counterbalances the tele-
scope. That’s the point at which the shaft remains horizontal
even when you let go of the telescope with both hands.
3. Retighten the counterweight lock bolt. The telescope is
now balanced on the R.A. axis.
4. To balance the telescope on the Dec. axis, first tighten the
R.A. lock bolt, with the counterweight shaft still in the
horizontal position.
5. With one hand on the telescope optical tube, loosen the
Dec. lock bolt. The telescope should now be able to rotate
freely about the Dec. axis. Loosen the knurled 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).
6. Position the telescope so that it remains horizontal when
you carefully let go with both hands. This is the balance
point. Before clamping the rings tight again, rotate the
telescope so the eyepiece is at a convenient angle for view-
ing. When you are actually observing with the
telescope, you can adjust the eyepiece position by
loosening the tube ring clamps and rotating the optical tube.
7. Retighten the knurled tube ring lock clamps.
The telescope is now balanced on both axes. Now when you
loosen the lock bolt 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 location
of objects for subsequent viewing through the main tele-
scope, which has a much narrower field of view. The finder
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 main telescope’s
focuser. Then loosen the R.A. and Dec. lock bolts so the
telescope can be moved freely.
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 eye-
piece. Now tighten the R.A. and Dec. lock bolts. Use the
slow-motion control knobs to recenter the object in the field of
view, if it moved off-center when you tightened the lock bolts.
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
that only fine adjustment of the 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.
Use the three 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.
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 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 2) is designed to compensate
for that motion, allowing you to easily “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, which is also called Polaris. It lies within 1° of the
north celestial pole (NCP), which is an extension of the
Earth’s rotational 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 3). 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° 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 lock t-bolt. Turn the latitude adjustment
t-bolt and tilt the mount until the pointer on the latitude
scale is set at the latitude of your observing site. If you
don’t know your latitude, consult a geographical atlas to
find it. For example, if your latitude is 35° North, set the
pointer to +35. Then retighten the latitude lock t-bolt. The
latitude setting should not have to be adjusted again
unless you move to a different viewing location some dis-
tance away.
3. Loosen the Dec. lock bolt and rotate the telescope optical tube
until it is parallel with the R.A. axis. The pointer on the Dec.
setting circle should read 90°. Retighten the Dec. lock bolt.
4. Loosen the azimuth lock knob and rotate the mount in
azimuth (left-to-right) so the telescope tube (and R.A.
axis) points roughly at Polaris. If you cannot see Polaris
directly from your observing site, consult a compass and
