Orion 102mm EQ - Manual (Page 9)

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Figure 7. For Northern Hemisphere observers, use the
lower set of numbers on the R.A. setting circle. The R.A.
coordinate indicator arrow is between the “R” and the
“A” on the plastic gear cover. The telescope (not shown)
is pointing north of the celestial equator, so the
approximate coordinates of the mount in the image are
R.A. 8h 30m Dec. 60°.
Finding Objects With the Setting Circles
Now that both setting circles are calibrated, look up in a star
atlas the coordinates of an object you wish to view.
1. Loosen the Dec. lock knob and rotate the telescope until
the Dec. value from the star atlas matches the reading on
the Dec. setting circle. Remember that values of the Dec.
setting circle are positive when the telescope is pointing
north of the celestial equator (Dec. = 0°), and negative
when the telescope is pointing south of the celestial equa-
tor. Retighten the lock knob.
2. Loosen the R.A. lock knob and rotate the telescope until
the R.A. value from the star atlas matches the reading on
the R.A. setting circle. Remember to use the lower set of
numbers on the R.A. setting circle. Retighten the lock knob.
Most setting circles are not accurate enough to put an object
dead-center in the telescope’s eyepiece, but they should
place the object somewhere within the field of view of the
finder scope, assuming the equatorial mount is accurately
polar aligned. Use the slow-motion controls to center the
object in the finder scope, and it should appear in the tele-
scope’s field of view.
The R.A. setting circle must be re-calibrated every time you
wish to locate a new object. Do so by calibrating the setting cir-
cle for the centered object before moving on to the next one.
Confused About Pointing the Telescope?
Beginners occasionally experience some confusion about how
to point the telescope overhead or in other directions. In Figure
1 the telescope is pointed north, as it would be during polar
alignment. The counterweight shaft is oriented downward. But
it will not look like that when the telescope is pointed in other
directions. Let’s say you want to view an object that is directly
overhead, at the zenith. How do you do it?
DO NOT make any adjustment to the latitude adjustment t-
bolt. That will nullify the mount’s polar alignment. Remember,
once the mount is polar aligned, the telescope should be
moved only on the R.A. and Dec. axes. To point the scope
overhead, first loosen the R.A. lock knob and rotate the tele-
scope on the R.A. axis until the counterweight shaft is
horizontal (parallel to the ground). Then loosen the Dec. lock
knob and rotate the telescope until it is pointing straight over-
head. The counterweight shaft is still horizontal. Then
retighten both lock knobs.
Similarly, to point the telescope directly south, the counter-
weight shaft should again be horizontal. Then you simply rotate
the scope on the Dec. axis until it points in the south direction.
What if you need to aim the telescope directly north, but at an
object that is nearer to the horizon than Polaris? You can’t do
it with the counterweight down as pictured in Figure 1. Again,
you have to rotate the scope in R.A. so the counterweight
shaft is positioned horizontally. Then rotate the scope in Dec.
so it points to where you want it near the horizon.
To point the telescope to the east or west, or in other direc-
tions, rotate the telescope on its R.A. and Dec. axes.
Depending on the altitude of the object you want to observe,
the counterweight shaft will be oriented somewhere between
vertical and horizontal.
Figure 8 illustrates how the telescope will look pointed at the
four cardinal directions—north, south, east, and west
The key things to remember when pointing the telescope is
that a) you only move it in R.A. and Dec., not in azimuth or lat-
itude (altitude), and b) in actual use the counterweight and
shaft will rarely appear as it does in Figure 1.
Dec. coordinate indicator arrow
Celestial equator (Dec. = 0°)
Use these numbers on
the R.A. setting circle
(Northern Hemisphere)
Plastic R.A. gear cover
R.A. coordinate indicator arrow