Orion ED EQ - Manual (Page 12)

12
Calibrating the right ascension Setting Circle
1. Identify a bright star in the sky near the celestial equa-
tor (declination = 0°) and look up its coordinates in a star
atlas.
2. Loosen the R.A. and Dec. lock levers on the equatorial
mount, so the telescope optical tube can move freely.
3. Point the telescope at the bright star whose coordinates
you know. Center the star in the telescope’s field of view.
Lock the R.A. and Dec. lock levers.
4. Loosen one of the R.A. setting circle thumb screws (see
Figure 13); this will allow the setting circle to rotate freely.
Rotate the setting circle until the R.A. pointer arrow indi-
cates the R.A. coordinate listed in the star atlas for the
object. Retighten the setting circle thumb screw.
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 lever and rotate the telescope until
the declination value from the star atlas matches the read-
ing on the Dec. setting circle. Remember that values of the
Dec. setting circle are positive when the telescope is point-
ing north of the celestial equator (Dec. = 0°), and negative
when the telescope is pointing south of the celestial equa-
tor. Retighten the lock lever.
2. Loosen the R.A. lock lever and rotate the telescope until the
right ascension value from the star atlas matches the read-
ing on the R.A. setting circle. Remember to use the lower
set of numbers on the R.A. setting circle. Retighten the lock
lever.
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 telescope’s field
of view.
The setting circles must be re-calibrated every time you wish
to locate a new object. Do so by calibrating the setting circles
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 down-
ward. 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 L-
bolts. That will spoil 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 lever and rotate the tele-
scope on the right ascension axis until the counterweight
shaft is horizontal (parallel to the ground). Then loosen the
Dec. lock lever and rotate the telescope until it is pointing
straight overhead. The counterweight shaft is still horizontal.
Then retighten both lock levers.
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 right ascension so that the
counterweight shaft is positioned horizontally. Then rotate the
scope in declination so it points to where you want it near the
horizon.
To point the telescope directly south, the counterweight shaft
should again be horizontal. Then you simply rotate the scope
on the declination axis until it points in the south direction.
To point the telescope to the east or west, or in other direc-
tions, you rotate the telescope on its right ascension and
declination axes. Depending on the altitude of the object you
want to observe, the counterweight shaft will be oriented
somewhere between vertical and horizontal.
Figure 14 illustrates how the telescope will look when pointed
at the four cardinal directions: north, south, east and west.
7. astronomical observing
For many users, the SkyView Pro 100mm ED EQ telescope
will be a major leap into the world of amateur astronomy. This
section is intended to get you ready for your voyages through
the night sky.
Site Selection
Pick a location away from street lights and bright yard light-
ing. Avoid viewing over rooftops and chimneys, as they often
Figure 14a-d. This illustration shows the telescope pointed in
the four cardinal directions (a) north, (b) south, (c) east, (d) west.
Note that the tripod and mount have not been moved; only the
telescope tube has been moved on the R.A. and Dec. axes.
a b
c d