Orion EQ-G instruction manual Setting Up and Using the Equatorial Mount

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.

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

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.

Dec. lock lever (not shown)

Front opening			(RRight
				Ascension
			.
			A
			.
			)
			axis
	(Dec)		axis
Declination
		adjustment
			Azimuth
			knobs (2)

Figure 5. The Atlas EQ-G mount.

R.A. lock lever

Polar axis finder scope

Latitude scale

Latitude adjustment L-bolts

a.b.

c.d.

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.

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 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.

	Little Dipper
	(in Ursa Minor)
Big Dipper	N.C.P.
(in Ursa Major)		Polaris
Pointer		Cassiopeia
Stars

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).

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