What is IERS Reference frame?

Question

I'm working on an astrological programming task & I want to know what this IERS Reference frame is. It's a reference frame, that much I get, but how is it defined?

Answer 1

IERS is the International Earth Rotation Service. They work with 2 reference frames, the International Terrestrial Reference Frame (ITRF) and the International Celestial Reference Frame (ICRF). The ITRF is used for measurement of phenomena such as the earth's rotation and polar wandering. The ICRF, which is more likely to be what you want, is the system of Right Ascension and Declination of celestial objects based on the equinox and equator of 2000 (designated J2000.0). Most almanac data for planets uses the equinox and equator of date rather than the fixed equinox J2000.0. The difference between the two takes into account precession of the Earth's axis. This causes the mean equinox to depart from a fixed equinox by approximately 50 arcseconds per year, or 1 degree in 72 years. If you're just interested in the celestial longitude of planets, measured along the ecliptic, then simply subtract 50 arcseconds per year to convert from the equinox of date to equinox J2000.0.

Answer 2

Google it!