Quadrants are described using ordinals—for example, "1st galactic quadrant" "second galactic quadrant," or "third quadrant of the Galaxy." Viewing from the north galactic pole with 0 degrees as the ray that runs starting from the Sun and through the galactic center, the quadrants are as follows :
1st galactic quadrant – 0° ≤ ≤ 90°
2nd galactic quadrant – 90° ≤ ≤ 180°
3rd galactic quadrant – 180° ≤ ≤ 270°
4th galactic quadrant – 270° ≤ ≤ 360°
Constellations grouped by galactic quadrants
Quad
Constellations
NGQ1
7
SGQ1
11
NGQ2
8
SGQ2
11
NGQ3
8
SGQ3
9
NGQ4
12
SGQ4
22
Visibility of each quadrant
Due to the orientation of the Earthwith respect to the rest of the Galaxy, the 2nd galactic quadrant is primarily only visible from the northern hemisphere while the 4th galactic quadrant is mostly only visible from the southern hemisphere. Thus, it is usually more practical for amateur stargazers to use the celestial quadrants. Nonetheless, cooperating or international astronomical organizations are not so bound by the Earth's horizon. Based on a view from Earth, one may look towards major constellations for a rough sense of where the borders of the quadrants are:
A long tradition of dividing the visible skies into four precedes the modern definitions of four galactic quadrants. Ancient Mesopotamian formulae spoke of "the four corners of the universe" and of "the heaven's four corners", and the Biblical Book of Jeremiah echoes this phraseology: "And upon Elam will I bring the four winds from the four quarters of heaven". Astrology too uses quadrant systems to divide up its stars of interest. And the astronomy of the location of constellations sees each of the Northern and Southern celestial hemispheres divided into four quadrants.
In fiction
''Star Trek''
"Galactic quadrants" within Star Trek are based around a meridian that runs from the center of the Galaxy through Earth's solar system, which is not unlike the system used by astronomers. However, rather than have the perpendicularaxis run through the Sun, as is done in astronomy, the Star Trek version runs the axis through the galactic center. In that sense, the Star Trekquadrant system is less geocentric as a cartographical system than the standard. Also, rather than use ordinals, Star Trek designates them by the Greek letters Alpha, Beta, Gamma, and Delta. The CanadianGalactic Plane Survey created a radio map of the Galaxy based on Star Treks quadrants, joking that "the CGPS is primarily concerned with Cardassians, while the SGPS focuses on Romulans."
''Star Wars''
"Galactic quadrants" within Star Wars canon astrography map depicts a top-down view of the galactic disk, with "Quadrant A" as the side of the galactic center that Coruscant is located on. As the capital planet of the Republic and later the Empire, Coruscant is used as the reference point for galactic astronomy, set at XYZ coordinates 0-0-0. Standardized galactic time measurements are also based on Coruscant's local solar day and year.
''Warhammer 40000''
The Imperium of Man's territory in the Milky Way Galaxy in Warhammer 40000 is divided into five zones, known as "segmentums". Navigation in the Milky Way is also identified with cardinal directions, indicating distance from the Sol System: for example, Ultima Segmentum, the largest segmentum in the Imperium of Man, is located to the galactic east of the Sol System.
