User`s guide

Appearance of the Sky 57
passing through the constellations of the
zodiac over the course of a year. Because
the planets all move in almost the same
plane, with the exception of Pluto, they
will all be found close to the ecliptic line.
Ecliptic longitude has the vernal equinox
as its zero point.
Galactic: This system uses the centre of
the Milky Way as a reference point. Its
co-ordinates are galactic latitude and
galactic longitude. Galactic latitude
describes how far an object is from the
plane of the Milky Way (an object with a
galactic latitude of 0° is in the plane of the
Milky Way). The zero point of galactic
longitude points directly toward the
galaxy’s centre.
Extra-Galactic: The co-ordinates of this
system are extra-galactic latitude and
longitude. A large fraction of the nearest
few thousand galaxies from Earth are
concentrated in a narrow band. The centre
of this band is defined as the plane of 0°
extra-galactic latitude, the extra-galactic
equator.
Guides 2 (Display Options)
Now that you know what each of the
different co-ordinate systems are, let’s
look at the options for displaying markers
for these systems. Recall that all of these
options are in the “Guides” layer of the
Options pane.
The Guides display looks very different in
Starry Night Enthusiast compared to
Starry Night Pro and Pro Plus. First we’ll
look at the” Guides Layer” in Enthusiast.
Skip to the next section if you are using
Starry Night Pro or Pro Plus.
Guides Layer in Enthusiast
The Guides layer in the Options pane
allows you to display reference points for
different astronomical co-ordinate
systems. These reference points can be
used to help you identify the position of
objects in the sky.
Celestial Grid: The celestial grid shows the
gridlines of the Equatorial co-ordinate
system mapped onto the sky. See “Position
in Space” on page 69 for a description of
the equatorial co-ordinate system.
Celestial Poles: The North and South
Celestial Poles
are projections into space
of Earth’s north and south poles. Polaris,
the North Star, is very close in the sky to
the North Celestial Pole.
Local Meridian: The local meridian is an
imaginary line running from due north
along the horizon through the zenith,
through to due south along the horizon.
During a given night, a celestial object will