Orion SKYQUEST XX12 - Manual (Page 23)

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in which it resides, its right ascension and declination coordi-
nates, the object type, magnitude, angular size, as well as a
brief description in scrolling text.
The IntelliScope Object Locator is a wonderful convenience
for both the novice and experienced observer. You’ll spend
more time actually observing astronomical objects instead
of hunting for them. For instructions on how to operate the
Object Locator, refer to the instruction manual included in the
box with the IntelliScope Object Locator kit.
selecting an observing site
Since most astronomical objects are faint, observing them
from dark skies will give you the best views. While some
objects, such as the planets and Moon, are bright enough
to see clearly even from light-polluted city skies, for nebulas,
galaxies, and most star clusters, the less ambient light there
is to reduce contrast, the better.
When it isn’t possible or convenient to get out of town to a
pitch-black observing location, try to set up in a spot that is
removed from street and building lights and that has a clear
view of a large portion of the sky. Avoid pointing the tele-
scope above buildings, if possible, since they radiate heat
which degrades images. For observing faint deep sky objects,
choose a moonless night. Using the optional light shroud will
be a necessity (see below). Also, use of a light-pollution fil-
ter, like the Orion SkyGlow Broadband filter, can mitigate the
effects of background sky brightness, enhancing the view of
faint objects.
use of the optional light shroud
When viewing from light-polluted skies, we highly recommend
using the optional light shroud for the XX12. The light shroud is
a black nylon cloth wrap which fits over the exterior of the truss
poles (Figure 41). The shroud prevents stray light from entering
the telescope through the open truss section of the tube and degrading image contrast. The shroud also helps prevent dew
from forming on the optical surfaces of the telescope.
seeing and transparency
Atmospheric conditions play a huge part in quality of viewing.
Light from stars and other celestial objects must travel through
miles of Earth’s atmosphere to reach our eyes. The air in the
atmosphere will refract and bend the light. Atmospheric turbu-
lence will worsen the effects of refraction, which can cause the
image you see in your telescope to be unstable. The steadi-
ness of the atmosphere is called the “seeing” condition.
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 conditions generally
get better later in the evening, as much of the heat absorbed
by the Earth during the day has radiated off into space. In
conditions of bad seeing, stars will twinkle and objects will
appear unsteady and blurry in the telescope.
“Transparency” is the clarity of the atmosphere, which can
be adversely affected by the presence of moisture, smoke,
and dust. All tend to scatter light, which reduces an object’s
brightness. Good transparency is desirable for astronomical
observing, especially for viewing faint objects.
One good measure of transparency is by how many stars
you can see with your unaided eyes. If you cannot see stars
of magnitude 3.5 or dimmer, then transparency is poor.
Magnitude is a measure of how bright a star is. The brighter
a star, the lower its magnitude. A good star to remember for
this is Megrez (magnitude 3.4), which is the star in the Big
Dipper that connects the handle to the “dipper.” If you can-
not see Megrez, then you have fog, haze, clouds, smog, light
pollution or other conditions which are hindering your viewing
(Figure 42).
Figure 41. The optional light shroud for the XX12 prevents stray
light from entering the telescope. It also helps prevent dew from
forming on the optical surfaces.
1.9
1.9
1.7
4.9
2.4 3.4
2.5
2.4
Figure 42. Megrez connects the Big Dipper’s handle to it’s “pan”.
It is a good guide to judging the transparency of the night sky. If you
cannot see Megrez (a 3.4-magnitude star) then transparency is poor.