Applet: Sky Precession
Precession and Proper Motion Applet
Input field: green
Algorithm from J. Meeus ("Astronomical Algorithms", Chapter 20: Precession).
The current standard epoque is "J2000" (2000, Jan 1 at 12 h TD), corresponding to JD 2 451 545.0. For purposes of calculating positions of stars, the beginning of a "year" differs from the standard epoque J2000.0 by an integer multiple of the Julian year (365.25 days).
Noon on January 1, -4712, i.e., January 1, 4713 BC (JD 0) is J-4711.96441
mean tropical year 365.24219 SI days
In case the proper motion in RA is given in
seconds (s), the value has to be multiplied by 15 to
get arcseconds (as)
The results of my applet agree with those of
The coordinates (Ra, Dec) are also converted to ecliptic values (long. L, lat. B)
© 2003-2013 J. Giesen
Updated: 2013 Jun 15