Program  NERS_AZELHA  computes azimuth, elevation, hour angle,
as well as their time derivatives at moment of time TIM_TAI for 
a station with coordinates in the crust-fixed terrestrial coordinate 
system COO_TRS that observes a source with coordinates in the 
barycentric celestial coordinate system RA, DEC. Both annual and 
diurnal aberrations are taken into account. Elevation is computed 
with respect to the normal to the reference ellipsoid. Vertical 
deflection is ignored. Optionally the elevation can be corrected 
for refraction.
 
This program can be used only for computation of azimuths, elevations
and hour angles of an object beyond the Solar system, such a as 
a star or a galaxy.
 
Usage: ners_azelha date coo_trs ra dec [none|optic|radio]
 
where date is the date in YYYY.MM.DD_hh:mm:ss.sss format or now,
      coo_trs is the vector of station coordinates in the rotating
              crust-fixed coordinate system in meters,
      ra      is the right ascension of the observed body in rad;
      dec     is the declination of the observed body in rad;
      [none|optic|radio] is optional computation of refration:
                         none  -- not to account refraction,
                         optic -- to account refraction in optic
                                  range;
                         radio -- to account for refraction in
                                  radio range.
Units: radians for azimuth, elevation angle, and hour angle;
       rad/s for their time derivatives.