Orion ATLAS EQ-G User Manual download pdf (Page 5)

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.

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

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.

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.

a. b.

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).

Big Dipper

(in Ursa Major)

Little Dipper

(in Ursa Minor)

Cassiopeia

N.C.P.

Pointer

Stars

Polaris

Figure 5. The Atlas EQ-G mount.

Dec. lock lever

(not shown)

Front opening

R.A. lock lever

Polar axis

finder scope

Latitude scale

Latitude

adjustment L-bolts

Azimuth

adjustment

knobs (2)

Declination

(Dec) axis

Right Ascension

(R.A.) axis

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Orion ATLAS EQ-G User Manual Page 5

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