Celestron C4.5 User Manual

a ——
equilibrium. Once adjusted to the outdoor temperature, don’t touch the
telescope tube with your hands. When pointing the telescope, hold the C4.5
by the eyepiece holder. If observing with others, make sure no one stands in
front of or directly below the telescope tube.
The images produced by Type 2 seeing conditions don’t move as quickly as
those produced by Type 1 conditions, but the images are quite blurry. Fine
detail is lost and the contrast is low for extended objects. Stars are spread out
and not sharp. The source of Type 2 seeing is the lower atmosphere, most
likely heat waves from the ground or buildings. To avoid the problems
associated with Type 2 seeing, select a good observing site. Specifically,
avoid sites that overlook asphalt parking lots or plowed fields. Stay away
from valleys and shorelines. Instead, look for broad hill tops or open grassy
fields. Stable thermal conditions found near lakes and atmospheric inver-
sions also tend to produce good seeing. If you can't get a better location,
wait until the early morning hours when the surroundings are uniformly
cool and the seeing is generally better.
Type 3 seeing conditions are characterized by fast ripples, but sharp images.
In extended objects fine detail is visible, but the image shifts around the field.
Stars are crisp points, but they shift small distances rapidly around the field.
The cause of type 3 seeing is turbulence in the upper atmosphere which
means the observer has less control over it. However, the effects of Type 3
seeing are generally less pronounced than the other two types. You can
never really avoid Type 3 seeing. Your best bet is to wait until moments of
steadiness. If the seeing is extremely bad, pack up and wait for a better
night.
The conditions described here apply to both visual and photographic obser-
vations.
Figure 6-4
Seeing conditions directly affect image quality. These drawings repre-
sent a point source (i.e., star) under bad seeing conditions (left) to
excellent conditions (right). Most often, seeing conditions produce
images that lie somewhere between these two extremes.
Celestial Observing + 39

Celestron C4.5 Specifications

General

Brand	Celestron
Model	C4.5
Category	Telescope
Language	English