old_contents: """
  ============================================
  Helioprojective/AltAz Coordinate Conversions
  ============================================
  
  This is a very simple example to show how to convert
  Helioprojective Coordiantes to Altitude/Azimuth Coordinates.
  In this example, we use balloons observations to include
  elevation as a factor.
  """
  from astropy.coordinates import EarthLocation, AltAz, SkyCoord
  from astropy.time import Time
  from sunpy.coordinates import frames, get_sunearth_distance
  import astropy.units as u
  
  ######################################################################################
  # We use `~astropy.coordinates.SkyCoord` to define the center of the Sun
  time = "2013-09-21 16:00:00"
  c = SkyCoord(0 * u.arcsec, 0 * u.arcsec, obstime=time, frame=frames.Helioprojective)
  
  ######################################################################################
  # Now we establish our location on the Earth, in this case Fort Sumner, NM.
  # We use the balloon's observational altitude as 'height'. Accuracy of 'height' is
  # far less of a concern than Lon/Lat accuracy.
  Fort_Sumner = EarthLocation(lat=34.4900*u.deg, lon=-104.221800*u.deg, height=40*u.km)
  
  ######################################################################################
  # Now lets convert this to a local measurement of Altitude and Azimuth.
  
  frame_altaz = AltAz(obstime=Time(obstime), location=Fort_Sumner)
  sun_altaz = c.transform_to(frame_altaz)
  print('Altitude is {0} and Azimuth is {1}'.format(sun_altaz.T.alt, sun_altaz.T.az))
  
  ######################################################################################
  # Next let's check this calculation by converting it back to helioprojective.
  # We should get our original input which was the center of the Sun.
  # To go from Altitude/Azimuth to Helioprojective, you will need the distance to the Sun.
  # solar distance. Define distance with SunPy's almanac.
  distance = get_sunearth_distance(obstime)
  b = SkyCoord(az=sun_altaz.T.az, alt=sun_altaz.T.alt, distance=distance, frame=frame_altaz)
  sun_helio = b.transform_to(frames.Helioprojective)
  print('The helioprojective point is {0}, {1}'.format(sun_helio.T.Tx, sun_helio.T.Ty))
  
  ######################################################################################
  # The output is within a radius of 0.02 arcseccs.
  
new_contents: """
  ============================================
  Helioprojective/AltAz Coordinate Conversions
  ============================================
  
  This is a very simple example to show how to convert
  Helioprojective Coordiantes to Altitude/Azimuth Coordinates.
  In this example, we use balloons observations to include
  elevation as a factor.
  """
  from astropy.coordinates import EarthLocation, AltAz, SkyCoord
  from astropy.time import Time
  from sunpy.coordinates import frames, get_sunearth_distance
  import astropy.units as u
  
  ######################################################################################
  # We use `~astropy.coordinates.SkyCoord` to define the center of the Sun
  obstime = "2013-09-21 16:00:00"
  c = SkyCoord(0 * u.arcsec, 0 * u.arcsec, obstime=obstime, frame=frames.Helioprojective)
  
  ######################################################################################
  # Now we establish our location on the Earth, in this case Fort Sumner, NM.
  # We use the balloon's observational altitude as 'height'. Accuracy of 'height' is
  # far less of a concern than Lon/Lat accuracy.
  Fort_Sumner = EarthLocation(lat=34.4900*u.deg, lon=-104.221800*u.deg, height=40*u.km)
  
  ######################################################################################
  # Now lets convert this to a local measurement of Altitude and Azimuth.
  
  frame_altaz = AltAz(obstime=Time(obstime), location=Fort_Sumner)
  sun_altaz = c.transform_to(frame_altaz)
  print('Altitude is {0} and Azimuth is {1}'.format(sun_altaz.T.alt, sun_altaz.T.az))
  
  ######################################################################################
  # Next let's check this calculation by converting it back to helioprojective.
  # We should get our original input which was the center of the Sun.
  # To go from Altitude/Azimuth to Helioprojective, you will need the distance to the Sun.
  # solar distance. Define distance with SunPy's almanac.
  distance = get_sunearth_distance(obstime)
  b = SkyCoord(az=sun_altaz.T.az, alt=sun_altaz.T.alt, distance=distance, frame=frame_altaz)
  sun_helio = b.transform_to(frames.Helioprojective)
  print('The helioprojective point is {0}, {1}'.format(sun_helio.T.Tx, sun_helio.T.Ty))
  
  ######################################################################################
  # The output is within a radius of 0.02 arcseccs.
  
subject: Define obstime