Setting Up And Using The Equatorial Mount - Orion EQ-1 Equatorial Mount 9011 Instruction Manual

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
3d). Position the telescope so that it remains horizontal
when you carefully let go with both hands. This is the
balance point for the Dec. axis (Figure 3e). Before
clamping the rings tight again, rotate the telescope so
that the eyepiece is at a convenient angle for viewing.
Figure 3d. Balancing the telescope with respect to the Dec.
axis. As shown here, the telescope is out of balance (tilting).
Figure 3e. Telescope is now balanced on the Dec.
axis, i.e., it remains horizontal when hands
are released.
The telescope is now balanced on both axes. Now when
you loosen the lock thumb screw 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
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 2) is designed to compensate for that
motion, allowing you to easily "track" the movement of
astronomical objects, thereby keeping them from drift-
ing 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;
this is 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° 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 pat-
tern 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 fortu-
nate 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
alignment 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, con-
sult 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 thumb screw 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 thumb screw.