Coordinates

• Show RA/Dec grid: displays the right ascension/declination grid.

Note

The right ascension, noted a, α, AD (in French) or RA (in English, for Right Ascension), is one of the two terms associated with the equatorial coordinate system with declination. It is the equivalent on the celestial sphere of the earth’s longitude.

• Show Az/Alt grid: displays the Azimuth/Altitude grid.

Note

In astronomy, in the horizontal coordinate system (local system), the direction of a celestial object can be given by its azimuth, horizontal angle measured from the South meridian clockwise, and its altitude: the advantage is that when it passes the meridian, both the azimuth and the hour angle of a star are zero.

• Show cardinal points: displays North, South, East, West labels.
• Show the celestial equator:

Note

The celestial equator is a large circle drawn on the celestial sphere which is the projection of the terrestrial equator on it.

• Show the ecliptic:

Note

From a geocentric point of view, the ecliptic is the large circle representing the projection, on the celestial sphere, of the apparent annual trajectory of the Sun seen from the Earth. From a heliocentric point of view, it is the intersection of the celestial sphere with the ecliptic plane (geometric plane containing the Earth’s orbit around the Sun). The plane of the ecliptic is the reference plane of the celestial coordinate system known as the ecliptic coordinate system.