Orion 9829 - Manual (Page 5)

4. To balance the telescope on the declination axis, first tight-
en the R.A. lock lever, with the counterweight shaft still in
the horizontal position.
5. With one hand on the telescope optical tube, loosen the
Dec. lock lever. 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 3c).
6. Position the telescope in the tube rings so it remains hori-
zontal when you carefully let go with both hands. This is
the balance point for the optical tube with respect to the
Dec. axis (Figure 3d).
7. Retighten the knurled ring clamps.
The telescope is now balanced on both axes. When you
loosen the lock lever on one or both axes and manually point
the telescope, it should move without resistance and should
not drift from where you point it.
6. 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 4) is
designed to compensate for that motion, allowing you to easi-
ly “track” the movement of astronomical objects, thereby
keeping them from drifting out of your telescope’s field of view
while you’re observing.
This is accomplished by slowly rotating the telescope on its
right ascension (R.A.) axis, using only the R.A. slow-motion
knob. 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 align-
ment is achieved by pointing the mount’s right ascension axis
at the North Star, or Polaris. It lies within 1° of the north celes-
tial pole (NCP), which is an extension of the Earth’s rotational
axis out into space. Stars in the Northern Hemisphere appear
to revolve around the NCP.
To find Polaris in the sky, look north and locate the pattern of
the Big Dipper (Figure 5). 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 bare-
ly 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.
5
Figure 4. The SkyView Pro Equatorial Mount, shown from both sides.
Dec. slow-motion
control knob
Dec. setting circle
Front opening
R.A. slow-motion
control knob
a. b.
R.A.
setting circle
Polar axis
finder scope
(optional)
Dec. lock lever
R.A. lock lever
Latitude scale
Latitude
adjustment
L-bolts
Figure 5. To find Polaris in the night sky, look north and find the
Big Dipper. Extend an imaginary line from the two "Pointer Stars" in
the bowl of the Big Dipper. Go about five times the distance
between those stars and you'll reach Polaris, which lies within 1° of
the north celestial pole (NCP).
Big Dipper
(in Ursa Major)
Little Dipper
(in Ursa Minor)
Cassiopeia
N.C.P.
Poin
ter
Stars
Polaris