For a given date and time, GET_RB0P returns the
solar radius, solar B-angle, and p angle for that time.
This routine used to be called PB0R, but GET_RB0P can handle
any of the three standard time formats.
IDL> rb0p = get_rb0p('15-nov-91')
IDL> rb0p = get_rb0p(index)
If N input times are passed in, then the output is 3xN where
rb0p(0) is (R) solar radius in arcseconds measured outside earth's atmosphere,
rb0p(1) is (B-angle) heliographic latitude of the central point of the
solar disk, and
rb0p(2) is (P) position angle of the northern extremity of the axis
of the sun's rotation, measured eastward from the
geographic north point of the solar disk.