Astrophysics (Index)About

equatorial coordinate system

(EQ)
(latitude/longitude-like system for the celestial sphere)

The equatorial coordinate system is a spherical coordinate system used for directions into the celestial sphere, fixed to the stars/constellations as seen from Earth. Equatorial coordinates (EQ) are aligned with Earth's equator and poles: Elements:

For example, a point in the celestial sphere which is at the zenith (i.e., straight up) over some point on Earth's equator (i.e., with latitude 0°) has a declination of 0% and points similarly over the north pole (latitude 90° north) has a declination of +90°. However the relationship between right ascension and longitude shifts with time, its most obvious shift occurring over a daily cycle. In contrast, the relationship between declination and latitude is basically constant.

The equatorial coordinate system (and the closely related International Celestial Reference System, IRCS) is commonly used to describe the positions of planets in the celestial sphere at some particular point in time, and its coordinates are commonly used for identifying and naming objects beyond the solar system (e.g., J designators), which change coordinates far more slowly.

The Earth's precession of the equinoxes slowly changes the equatorial coordinates of points on the celestial sphere, on the order of an arcsecond per month. This is a primary reason for specifying an epoch.


(coordinate system,equatorial,celestial sphere,Earth)
Further reading:
https://en.wikipedia.org/wiki/Equatorial_coordinate_system
https://astronomy.swin.edu.au/cosmos/e/equatorial+coordinate+system
http://hyperphysics.phy-astr.gsu.edu/hbase/eclip.html#c6
https://dictionary.obspm.fr/index.php?formSearchTextfield=equatorial+coordinate+system&showAll=1
http://spiff.rit.edu/classes/phys445/lectures/radec/radec.html
https://lco.global/spacebook/sky/equatorial-coordinate-system/
PrefixExample  
EQEQ J221734.0+001701abbreviationhttps://cds.unistra.fr/cgi-bin/Dic-Simbad?/4779023

Referenced by pages:
Catalogues of Fundamental Stars
celestial coordinate system
celestial pole
celestial reference frame
celestial sphere
declination (dec)
ecliptic
ephemeris
epoch
epoch J2000.0
equinox
Extended Groth Strip (EGS)
galactic coordinate system (GCS)
Groth Strip
International Celestial Reference System (ICRS)
J designator
J2000.0 equinox
precession of the equinoxes
right ascension (RA)
stellar designation
supergalactic coordinate system
zenith

Index