Orion ED EQ - Manual (Page 8)

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tions, 2" eyepieces can give a wider field of view than standard
1.25" eyepieces. This is especially desirable for observing
deep-sky objects, as many of them appear quite large, but
faint. Many observers own at least one 2" eyepiece in order to
achieve the widest field of view possible for deep sky-observ-
ing. The expansive view will make you feel like you’re floating
in space!
To use 2" eyepieces, simply loosen the thumb screw on the
star diagonal that secures the 1.25" adapter, and remove the
adapter. Insert a 2" eyepiece directly into the diagonal, and
secure it in place with the thumb screw on the diagonal. You
are now ready to observe with the 2" eyepiece. If you attempt
to place a 2" eyepiece directly into the focuser drawtube with-
out using the star diagonal, images will not come into focus. If
you wish to view with 2" eyepieces without using the diagonal,
you will need to purchase an optional 2" extension tube.
use of 1.25” Eyepieces without a Diagonal
The SkyView Pro 100mm ED can use 1.25" eyepieces with-
out a 90° star diagonal if desired. Viewing straight through the
telescope may be more comfortable for observing objects low
on the horizon. When viewing straight through the telescope
without a diagonal the view will be oriented the same as the
finder scope (rotated 180°, see Figure 7).
To use a 1.25” eyepiece without a diagonal, remove the 2"
diagonal by first loosening the two thumb screws on the fo-
cuser drawtube. Insert the camera adapter and secure it by
tightening the drawtube’s thumb screws. Loosen the thumb
screw on the camera adapter and insert the barrel of a 1.25"
eyepiece into it. Secure the eyepiece with the thumb screw on
the camera adapter.
note about Chromatic aberration
Chromatic aberration literally means color distortion. Whenever
light passes through one material to another, light of differ-
ent wavelengths (color) is bent by different amounts. This is
a problem that plagues refractor-type telescopes, since light
passes through both air and glass to form an image. Most
astronomical objects emit a spectrum comprised of many dif-
ferent wavelengths of light, so each wavelength will be bent by
a slightly different amount when passing through a lens. This
results in each color of light reaching precise focus at a slightly
different point, which will provide unacceptable images.
The 100mm ED is designed to minimize chromatic aberra-
tion. The objective lens is actually comprised of two individual
lenses, called elements, one of which is made of ED (Extra-
low Dispersion) glass, a special type of glass that has superior
refractive properties when compared to normal types of optical
glass. The use of this ED glass minimizes the amount of chro-
matic aberration, resulting in a much more pleasing view when
compared to telescopes that do not use ED glass.
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 8) is designed to compen-
sate 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 only the R.A. slow-motion 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.
Figure 8. The SkyView Pro mount.
R.A. setting circle
Polar axis finder scope
(optional)
Latitude scale
(opposite side)
Latitude
adjustment
L-bolts
Dec. slow-motion
control knob
Dec. setting circle
Dec. lock lever
Front opening
R.A. lock lever
R.A. slow-motion
control knob
Declination
Axis
Right
Ascension Axis