Collimation (Aligning The Mirrors) - Orion 8 EQ Instruction Manual

a.
Figure 13.
This illustration show the telescope pointed in the the four cardinal directions (a) north, (b) south, (c) east, (d) west. Note that
the tripod and moutn have ot been moved; only the telescope tube has been moved on the R.A. and Dec. axes.
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 find-
er 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.
a.
b.
b.
Figure 14.
Collimating the optics. (a) When the mirrors are properly aligned, the view
down the focuser drawtube should look like this (b) With the collimation cap in place, if the
optics are out of alignment, the view might look something like this. (c) Here, the secondary
mirror is centered under the focuser, but it needs to be adjusted (tilted) so that the entire
primary mirror is visible. (d) The secondary mirror is correctly aligned, but the primary mirror
still needs adjustment. When the primary mirror is correctly aligned, the "dot" will be centered,
as in (e).
c.
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 counterweights 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 13 illustrates how the telescope will look when pointed
at the four cardinal directions: north, south, east and west.
7. Collimation
(Aligning The Mirrors)
Collimation is the process of adjusting the mirrors so they are
perfectly aligned with one another. Your telescope's optics
were aligned at the factory, and should not need much adjust-
ment unless the telescope is handled roughly. Accurate mirror
alignment is important to ensure the peak performance of
your telescope, so it should be checked regularly. Collimation
is relatively easy to do and can be done in daylight.
c. d.
d.
e.
11