Table 1 A comparison with optical refraction given by Allen (AQ3)

 Wavelength          0.55mm 
 Observer Height     0.0 km
 Ambient temperature 10degC
         pressure    760mmHg
         humidity    90%

 Refraction from model atmosphere calculations

     Zenith       Refraction   AQ3      Diff
     Distance
        o            "          "        "

        0           0.0         0       0.0
       10          10.4        10       0.4
       20          21.4        21       0.4
       30          33.9        34      -0.1
       40          49.2        49       0.2
       45          58.7        59      -0.3
       50          69.9        70      -0.1
       55          83.7        84      -0.3
       60         101.4       101       0.4
       65         125.3       125       0.3
       70         159.9       159       0.9
       75         215.7       215       0.7
       80         321.4       319       2.4
       81         355.1       353       2.1
       82         396.0       394       2.0
       83         446.7       444       2.7
       84         511.1       509       2.1
       85         594.9       593       1.9
       86         707.9       706       1.9
       87         866.1       865       1.1
       88        1099.0      1103      -4.0
       89        1466.3      1481     -14.7
       89.5      1740.7      1760     -19.3