13
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.
Seeing and transparency
Atmospheric conditions play a huge part in quality of view-
ing. In conditions of good “seeing”, star twinkling is minimal
and objects appear steady in the eyepiece. Seeing is best
overhead, 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 observ-
ing 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
for observing faint objects. 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 remember 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 pollution or other conditions that are
hindering your viewing (see Figure 15).
Cooling the telescope
All optical instruments need time to reach “thermal equilibri-
um” to achieve peak performance. When moved from a warm
indoor location to cooler outdoor air (or vice-versa), a tele-
scope needs time to acclimate 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 100mm ED
EQ to acclimate. If the scope has more than a 40° tempera-
ture change, 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 reach thermal equi-
librium. It also is a good idea to keep the scope covered until
the Sun sets so the tube does not heat greatly above the tem-
perature of the outside air.
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 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 automobile head-
lights 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 100mm ED
EQ. The telescope comes with two high-quality Sirius Plössl
eyepieces: a 25mm, which gives a magnification of 36x, and
a 10mm, which gives a magnification of 90x. Other eyepieces
can be used to achieve higher or lower powers. It is quite com-
mon for an observer to own five or more eyepieces to access
a wide range of magnifications. This allows the observer to
choose the best eyepiece to use depending on the object
being viewed. At least to begin with, the two supplied eye-
pieces will suffice nicely.
Whatever you choose to view, always start by inserting your
lowest power (longest focal length) eyepiece to locate and
center the object. Low magnification yields a wide field of
view, which shows a larger area of sky in the eyepiece. This
makes acquiring and centering an object much easier. If you
try to find and center objects with high power (narrow field of
view), it’s like trying to find a needle in a haystack!
Figure 15.
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 for observing faint objects.
