Orion SKYVIEW PRO 120 EQ - Manual (Page 12)

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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 dec-
lination axes. Depending on the altitude of the object you want
to observe, the counterweight shaft will be oriented some-
where between vertical and horizontal.
Figure 12 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 120 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.
observing tips
A. Site Selection
Pick a location away from street lights and bright yard light-
ing. Avoid viewing over rooftops and chimneys, as they often
have warm air currents rising from them, which distort the
image seen in the eyepiece. Similarly, you should not observe
through an open or closed window from indoors. Better yet,
choose a site out-of-town, away from any “light pollution”.
You’ll be stunned at how many more stars you’ll see! Most
importantly, make sure that any chosen site has a clear view
of a large portion of the sky.
B. Seeing and Transparency
Atmospheric conditions play a huge part in quality of viewing.
In conditions of good “seeing”, star twinkling is minimal and
objects appear steady in the eyepiece. Seeing is best over-
head, worst at the horizon. Also, seeing generally gets bet-
ter after midnight, when much of the heat absorbed by the
Earth during the day has radiated off into space. Typically,
seeing conditions will be better at sites that have an altitude
over about 3000 feet. Altitude helps because it decreases
the amount of distortion causing atmosphere you are looking
through.
A good way to judge if the seeing is good or not is to look at
bright stars about 40° above the horizon. If the stars appear to
“twinkle”, the atmosphere is significantly distorting the incom-
ing light, and views at high magnifications will not appear
sharp. If the stars appear steady and do not twinkle, seeing
conditions are probably good and higher magnifications will
be possible. Also, seeing conditions are typically poor during
the day. This is because the heat from the Sun warms the air
and causes turbulence.
Good “transparency” is especially important for observing faint
objects. It simply means the air is free of moisture, smoke, and
dust. All tend to scatter light, which reduces an object’s bright-
ness.
One good way to tell if conditions are good is by how many
stars you can see with your naked eye. If you cannot see
stars of magnitude 3.5 or dimmer then conditions are poor.
Magnitude is a measure of how bright a star is, the brighter a
star is, the lower its magnitude will be. A good star to remem-
ber for this is Megrez (mag. 3.4), which is the star in the “Big
Dipper” connecting the handle to the “dipper”. If you cannot
see Megrez, then you have fog, haze, clouds, smog, light pol-
lution or other conditions that are hindering your viewing (See
Figure 13).
C. Cooling the Telescope
All optical instruments need time to reach “thermal equilibrium”
to achieve maximum stability of the lenses, which is essential
for peak performance. When moved from a warm indoor loca-
Figure 12a‑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 been moved; only the telescope
tube has been moved on the R.A. and Dec. axes.
a b
c d
Figure 13. Megrez connects the Big Dipper’s handle to it's “pan”.
It is a good guide to how conditions are. If you can not see Megrez
(a 3.4 mag star) then conditions are poor.