def test_precession():
 j2000 = Time(u'J2000', scale=u'utc')
 b1950 = Time(u'B1950', scale=u'utc')
 j1975 = Time(u'J1975', scale=u'utc')
 b1975 = Time(u'B1975', scale=u'utc')
 fk4 = FK4(ra=(1 * u.radian), dec=(0.5 * u.radian))
 assert (fk4.equinox.byear == b1950.byear)
 fk4_2 = fk4.transform_to(FK4(equinox=b1975))
 assert (fk4_2.equinox.byear == b1975.byear)
 fk5 = FK5(ra=(1 * u.radian), dec=(0.5 * u.radian))
 assert (fk5.equinox.jyear == j2000.jyear)
 fk5_2 = fk5.transform_to(FK4(equinox=j1975))
 assert (fk5_2.equinox.jyear == j1975.jyear)

def test_precession ( ) : j2000 = Time ( u'J2000' , scale = u'utc' ) b1950 = Time ( u'B1950' , scale = u'utc' ) j1975 = Time ( u'J1975' , scale = u'utc' ) b1975 = Time ( u'B1975' , scale = u'utc' ) fk4 = FK4 ( ra = ( 1 * u . radian ) , dec = ( 0.5 * u . radian ) ) assert ( fk4 . equinox . byear == b1950 . byear ) fk4_2 = fk4 . transform_to ( FK4 ( equinox = b1975 ) ) assert ( fk4_2 . equinox . byear == b1975 . byear ) fk5 = FK5 ( ra = ( 1 * u . radian ) , dec = ( 0.5 * u . radian ) ) assert ( fk5 . equinox . jyear == j2000 . jyear ) fk5_2 = fk5 . transform_to ( FK4 ( equinox = j1975 ) ) assert ( fk5_2 . equinox . jyear == j1975 . jyear )
ensures that fk4 and fk5 coordinates precess their equinoxes .