Zon Mosaic Pro5 User's Guide Page 55

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Appearance of the Sky 55
You can draw stick
figures using either
the standard
astronomical figures,
or those popularized
by H.A. Rey in his book The Stars, a New
Way to See Them. These figures closely
resemble the names of the constellations.
For example, Ursa Major, the Great Bear,
is depicted as a stylized bear. To get the
figures to match the names, Rey had to
take some liberties, so it may be difficult
to match these figures to what you actually
see in the sky. You can also choose to draw
only the constellations of the Zodiac.
Finally, you can draw the asterisms, stick
figures that are not formal constellations.
It is also possible to create your own stick
figures. See “Custom Asterisms
” on
page 162 for information on creating your
own figures.
Note: It is not possible to view more than
one set of stick figures onscreen at the
same time.
By default Starry Night shows the
“Classical” image set for constellation
illustrations. If you have more than one set
of illustrations, you can select which one
to display from the “Image set” dropbox.
Guides 1 (Co-ordinate Systems)
The Guides layer in the Options pane
allows you to display reference points and
grids for different astronomical co-
ordinate systems. These co-ordinate
systems can be used to help you locate
objects in the sky. This section describes
the co-ordinate systems, while the next
section describes the options in the Guides
layer that control the display of these co-
ordinate systems.
Looking up into the night sky, you can
imagine that the stars are fixed on the
inside of an imaginary sphere surrounding
our planet. To specify locations on this
celestial sphere, astronomers use a
spherical system of co-ordinates similar to
the latitude and longitude measurements
used to map Earth.
All spherical co-ordinate systems require
two independent co-ordinates, which are
determined by an object’s distance in the
sky from two “great circles” which are
perpendicular to each other. For example,
the great circles in Earth’s latitude/
longitude co-ordinate system are the
Equator (which runs east-west) and the
Prime Meridian (which runs north-south).
The most commonly used systems are the
alt/az and equatorial systems. You may
also use ecliptic and, in Starry Night Pro
and Pro Plus, galactic and extra-galactic.
Tip (Pro and Pro Plus only): You can find
the co-ordinates of any object in any of
these co-ordinate systems using the Info
pane. See “Info Pane
” on page 90 for
more details.
Alt/Az: The alt/az co-ordinate system is
the most useful system for figuring out
where to actually look in the sky to find a
particular object. The two co-ordinates in
this system are the altitude and the
azimuth. The
altitude measures how high
above the horizon an object is, and is
usually measured in degrees. An altitude
of 0° means the object is right on the
horizon, and an altitude of 90° means the
object is directly overhead.
Azimuth
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