Setting Up And Using The Equatorial Mount - Orion 8 EQ Instruction Manual

Magnification is calculated as follows:
Telescope Focal Length (mm)
Eyepiece Focal Length (mm)
The SkyView Pro 8 EQ has a focal length of 1000mm, which
when used with the supplied 25mm eyepiece yields:
1000mm
The magnification provided by the 10mm eyepiece is:
1000mm
The maximum attainable magnification for a telescope is
directly related to how much light it can gather. The larger the
aperture, the more magnification is possible. In general a fig-
ure of 50x per inch of aperture is the maximum attainable for
most telescopes. Your SkyView Pro 8 EQ has an aperture of 8
inches, so the maximum magnification would be about 400x.
This level of magnification assumes you have ideal conditions
for viewing.
Keep in mind that as you increase magnification, the bright-
ness of the object viewed will decrease; this is an inherent
principle of the laws of physics and cannot be avoided. If mag-
nification is doubled, an image appears four times dimmer. If
magnification is tripled, image brightness is reduced by a fac-
tor of nine!
Start by centering the object being viewed in the 25mm eye-
piece. Then you may want to increase the magnification to get
a closer view. If the object is off-center (i.e., it is near the edge
of the field of view) you will lose it when you increase magnifi-
cation since the field of view will be narrower with the
higher-powered eyepiece. To change eyepieces, first loosen
the securing thumbscrew on the focuser. Then carefully lift the
eyepiece out of the holder. Do not tug or pull the eyepiece to
the sides, as this will knock the telescope off its target.
Replace the eyepiece with the new one by sliding it gently into
Dec. slow-motion
control knob
Dec. setting circle
Front opening
R.A. slow-motion
control knob
a.
= Magnification
= 40x
25mm
= 100x
10mm
R.A. setting
Polar axis finder
Latitude scale
adjustment
Figure 7. The SkyView Pro Equatorial Mount, shown from both sides.
the holder. Re-tighten the thumbscrew, and refocus for your
new magnification.
Using 2" eyepieces
The SkyView Pro 8 EQ's focuser is capable of accepting
optional 2" eyepieces. To use 2" eyepieces you must remove
the 1.25" adapter from the focuser by loosneing the two
thumbscrews that hold it in place. Once this adapter is
removed, insert a 2" eyepiece into the focuser and use the
same thumbscrews to secure the larger eyepiece.
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 7) is
designed to compensate for that motion, allowing you to easi-
ly "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 only the R.A. slow-motion
control knob. But first the R.A. axis of the mount must be
aligned with the Earth's rotational (polar) axis - a process
called polar alignment.
Polar Alignment
For Northern Hemisphere observers, approximate polar align-
ment is achieved by pointing the mount's right ascension axis
at the North Star, or Polaris. It lies within 1° of the north celes-
tial pole (NCP), which is an extension of the Earth's rotational
axis out into space. Stars in the Northern Hemisphere appear
to revolve around the NCP.
To find Polaris in the sky, look north and locate the pattern of
the Big Dipper (Figure 8). The two stars at the end of the
"bowl" of the Big Dipper point right to Polaris.
circle
scope
(optional)
Latitude
b.
L-bolts
Dec. lock lever
R.A. lock lever
7