Setting Up And Using The Equatorial Mount - Orion ATLAS EQ-G Manual

2. Now loosen both counterweight lock knobs and slide the
weights along the shaft until they exactly counterbalance
the telescope (Figure 4a). That's the point at which the
shaft remains horizontal even when you let go with both
hands (Figure 4b). If the telescope refuses to balance
than you have either too much or too little counterweight.
Remove a counterweight, or add optional counterweights
if needed.
3. Retighten the counterweight lock knobs. The telescope is
now balanced on the right ascension axis.
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 declination axis.
6. Loosen the knurled ring clamps on the tube rings 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 4c).
7. 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 4d).
8. Retighten the knurled ring clamps.
a.
c.
Figure 4a‑d.
Proper operation of the equatorial mount requires
that the telescope tube be balanced on the R.A. and Dec. axes. (a)
With the R.A. lock lever released, slide the counterweights down
the counterweight shaft until they just counterbalance the telescope
tube. (b) When you let go with both hands, the tube should not drift
up or down. (c) With the Dec. lock lever released, loosen the tube
ring lock clamps a few turns and slide the telescope forward or back
in the tube rings. (d) When the tube is balanced about the Dec. axis,
it will not move when you let go.
The telescope is now balanced on both axes. When you loos-
en 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
Dec. lock lever
(not shown)
Front opening
adjustment
Figure 5.
The Atlas EQ-G 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 5) is designed to
compensate for that motion, allowing you to easily "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
b.
right ascension (R.A.) axis, using the built in motor drive. But
first the R.A. axis of the mount must be aligned with the Earth's
rotational (polar) axis—a process called polar alignment.
d.
Big Dipper
(in Ursa Major)
Figure 6.
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).
Azimuth
knobs (2)
Little Dipper
(in Ursa Minor)
N.C.P.
Polaris
R.A. lock lever
Polar axis
finder scope
Latitude scale
Latitude
adjustment L-bolts
Cassiopeia
5