Astronomical Observing - Orion 8 EQ Instruction Manual

8. Astronomical Observing

For many users, the SkyView Pro 8 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 lighting.
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 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.
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 better
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 brightness.
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 20).
Cooling the Telescope
All optical instruments need time to reach "thermal equilibri-
um" to achieve maximum stability of the lenses and mirrors,
which is essential for peak performance. When moved from a
14
4.9
2.4
1.7
1.9
Figure 20.
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.
warm indoor location outside to cooler air (or vice-versa), a
telescope needs time to cool to the outdoor temperature. The
bigger the instrument and the larger the temperature change,
the more time will be needed.
Allow at least 30 minutes for your SkyView Pro 8 EQ to equili-
brate. If the scope has more than a 40° temperature
adjustment, allow an hour or more. In the winter, storing the
telescope outdoors in a shed or garage greatly reduces the
amount of time needed for the optics to stabilize. It also is a
good idea to keep the scope covered until the Sun sets so the
tube does not heat greatly above the temperature of the out-
side air.
You can attach a small fan to the SkyView Pro 8 EQ to make
cooling the tube faster. On the bottom of the mirror cell there
are four holes (M4 x. 7 thread) where a fan can be mounted.
Let Your Eyes Dark-Adapt
Do not expect to go from a lighted house into the darkness of
the outdoors at night and immediately see faint nebulas,
galaxies, and star clusters - or even very many stars, for that
matter. Your eyes take about 30 minutes to reach perhaps
80% of their full dark-adapted sensitivity. Many observers
notice improvements after several hours of total darkness. As
your eyes become dark-adapted, more stars will glimmer into
view and you will be able to see fainter details in objects you
view in your telescope. Exposing your eyes to very bright day-
light for extended periods of time can adversely affect your
night vision for days. So give yourself at least a little while to
get used to the dark before you begin observing.
To see what you are doing in the darkness, use a red-filtered
flashlight rather than a white light. Red light does not spoil
your eyes' dark adaptation like white light does. A flashlight
with a red LED light is ideal, or you can cover the front of a
regular incandescent flashlight with red cellophane or paper.
Beware, too, that nearby porch and streetlights and automo-
bile headlights will spoil your night vision.
Eyepiece Selection
By using eyepieces of varying focal lengths, it is possible to
attain many magnifications with the SkyView Pro 8 EQ. The
telescope comes with two high quality Sirius Plössl eyepieces:
1.9
2.4
3.4
2.5