Zon Mosaic Pro5 User's Guide download pdf (Page 59)

Appearance of the Sky 59

plane of Earth’s orbit around the Sun onto

the celestial sphere.

For the galactic system, available in Starry

Night Pro and Pro Plus, this is the galactic

equator, a line passing through the centre

of the band of the Milky Way.

Grid: Displays a grid with the latitude and

longitude gridlines for the co-ordinate

system in question. As you change your

field of view, the grid spacing will

automatically change. You can change the

default spacing of these gridlines in the

Guides Options dialog box.

Meridian: Displays the line of 0°

“longitude” for the co-ordinate system in

question. For the alt/az system, this is the

local meridian, a line running from due

north along the horizon through the zenith,

through to due south along the horizon.

For the equatorial system, available in

Starry Night Pro and Pro Plus, this is the

Celestial Meridian, the line of 0° right

ascension which passes through the Vernal

Equinox.

Poles: Displays markers for the points at

“latitudes” of 90° N and 90° S for the

co-ordinate system in question. For the alt/

az system, these are the zenith (the point in

the sky directly above your head) and the

nadir (the point directly below your feet).

For the equatorial system, these are

projections of Earth’s north and south

poles, known as the

North and South

Celestial poles

, respectively.

Vernal/Autumnal Equinox: Displays

markers for the Vernal and Autumnal

Equinoxes. The

Vernal Equinox is the

Sun’s position relative to the stars on the

first day of spring (in the Northern

Hemisphere), while the

Autumnal Equinox

is the Sun’s position relative to the stars on

the first day of fall. More precisely, they

are the Sun’s positions in the sky at the

two exact times when the plane of Earth’s

equator is the same as the plane defined by

Earth’s revolution around the Sun.

Summer/Winter Solstice: Displays

markers for the Summer and Winter

Solstices. The

Summer Solstice is the

Sun’s position relative to the stars on the

first day of summer (in the Northern

Hemisphere), while the

Winter Solstice is

the Sun’s position relative to the stars on

the first day of winter. More precisely,

they are the Sun’s positions in the sky at

the two exact times when the plane of

Earth’s equator is inclined at the largest

angle (about 23.5 degrees) to the plane

determined by Earth’s revolution around

the Sun.

Guides Options: Clicking on the words

“XXX Guides” in the Options pane will

open the Guides Options dialog box for

the co-ordinate system in question.

You can change the colour of the markers,

gridlines, and reference axes. You can also

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