Atmospheric Refraction Correction Table Observers Height Above MSL vs. Unrefracted Altitude Above Horizon Corrections in Arc-Minutes Toward the Zenith HEIGH TEMP PRESS ------ OBJECT ALTITUDE ABOVE HORIZON IN DEGREES ------ Feet DegC mbars 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 ----- ---- ------ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- 0 21.0 1070.0 34.8 29.0 24.6 21.2 18.5 16.3 14.6 13.1 11.9 10.9 10.0 1000 18.6 1034.5 33.9 28.3 24.0 20.6 18.0 15.9 14.2 12.8 11.6 10.6 9.7 2000 16.3 999.2 33.0 27.5 23.3 20.1 17.5 15.5 13.8 12.4 11.3 10.3 9.5 3000 13.9 964.3 32.1 26.8 22.7 19.6 17.1 15.1 13.4 12.1 11.0 10.0 9.2 4000 11.4 929.8 31.3 26.1 22.1 19.0 16.6 14.7 13.1 11.8 10.7 9.8 9.0 5000 9.0 896.1 30.4 25.3 21.5 18.5 16.1 14.2 12.7 11.4 10.4 9.5 8.7 6000 6.4 863.3 29.5 24.6 20.9 18.0 15.7 13.9 12.4 11.1 10.1 9.2 8.5 7000 3.9 831.5 28.7 23.9 20.3 17.5 15.2 13.5 12.0 10.8 9.8 9.0 8.2 8000 1.2 800.8 27.9 23.3 19.7 17.0 14.8 13.1 11.7 10.5 9.5 8.7 8.0 9000 -1.4 771.1 27.2 22.6 19.2 16.5 14.4 12.7 11.4 10.2 9.3 8.5 7.8 10000 -4.1 742.5 26.4 22.0 18.7 16.1 14.0 12.4 11.0 9.9 9.0 8.2 7.6 11000 -6.7 714.8 25.7 21.4 18.1 15.6 13.6 12.0 10.7 9.7 8.8 8.0 7.4 12000 -9.2 687.9 24.9 20.8 17.6 15.2 13.2 11.7 10.4 9.4 8.5 7.8 7.2 13000 -11.7 661.8 24.2 20.2 17.1 14.7 12.9 11.4 10.1 9.1 8.3 7.6 7.0 14000 -14.0 636.5 23.5 19.6 16.6 14.3 12.5 11.0 9.8 8.9 8.0 7.3 6.7 15000 -16.3 611.9 22.8 19.0 16.1 13.9 12.1 10.7 9.5 8.6 7.8 7.1 6.5 16000 -18.4 588.0 22.1 18.4 15.6 13.4 11.7 10.4 9.2 8.3 7.5 6.9 6.3 17000 -20.5 564.8 21.4 17.8 15.1 13.0 11.4 10.0 8.9 8.1 7.3 6.7 6.1 18000 -22.6 542.3 20.7 17.3 14.6 12.6 11.0 9.7 8.7 7.8 7.1 6.5 5.9 19000 -24.6 520.6 20.0 16.7 14.2 12.2 10.6 9.4 8.4 7.5 6.8 6.3 5.8 20000 -26.6 499.5 19.4 16.2 13.7 11.8 10.3 9.1 8.1 7.3 6.6 6.1 5.6 21000 -28.7 479.0 18.8 15.6 13.2 11.4 10.0 8.8 7.8 7.1 6.4 5.9 5.4 22000 -30.8 459.2 18.1 15.1 12.8 11.0 9.6 8.5 7.6 6.8 6.2 5.7 5.2 23000 -32.9 440.1 17.5 14.6 12.4 10.7 9.3 8.2 7.3 6.6 6.0 5.5 5.0 24000 -35.0 421.5 16.9 14.1 12.0 10.3 9.0 7.9 7.1 6.4 5.8 5.3 4.9 25000 -37.2 403.4 16.4 13.6 11.6 10.0 8.7 7.7 6.8 6.2 5.6 5.1 4.7 26000 -39.4 385.9 15.8 13.2 11.2 9.6 8.4 7.4 6.6 6.0 5.4 4.9 4.5 27000 -41.7 368.9 15.3 12.7 10.8 9.3 8.1 7.2 6.4 5.7 5.2 4.8 4.4 28000 -44.0 352.4 14.7 12.3 10.4 9.0 7.8 6.9 6.2 5.5 5.0 4.6 4.2 29000 -46.3 336.6 14.2 11.8 10.0 8.6 7.5 6.7 5.9 5.3 4.9 4.4 4.1 30000 -48.4 321.5 13.7 11.4 9.7 8.3 7.3 6.4 5.7 5.2 4.7 4.3 3.9 31000 -50.3 307.3 13.2 11.0 9.3 8.0 7.0 6.2 5.5 5.0 4.5 4.1 3.8 32000 -51.9 294.1 12.7 10.6 9.0 7.7 6.8 6.0 5.3 4.8 4.3 4.0 3.7 33000 -53.2 281.9 12.3 10.2 8.7 7.5 6.5 5.7 5.1 4.6 4.2 3.8 3.5 34000 -54.2 270.7 11.8 9.9 8.4 7.2 6.3 5.5 4.9 4.5 4.0 3.7 3.4 35000 -54.8 260.1 11.4 9.5 8.1 6.9 6.1 5.3 4.8 4.3 3.9 3.6 3.3 36000 -55.3 249.8 11.0 9.1 7.8 6.7 5.8 5.1 4.6 4.1 3.7 3.4 3.1 37000 -55.5 239.2 10.5 8.8 7.4 6.4 5.6 4.9 4.4 4.0 3.6 3.3 3.0 38000 -55.7 227.9 10.0 8.4 7.1 6.1 5.3 4.7 4.2 3.8 3.4 3.1 2.9 39000 -55.9 215.5 9.5 7.9 8.7 5.8 5.0 4.5 4.0 3.6 3.2 3.0 2.7 40000 -56.1 206.2 9.1 7.6 6.4 5.5 4.8 4.3 3.8 3.4 3.1 2.8 2.6 41000 -56.2 199.0 8.8 7.3 6.2 5.3 4.7 4.1 3.7 3.3 3.0 2.7 2.5 42000 -56.4 191.4 8.5 7.0 6.0 5.1 4.5 4.0 3.5 3.2 2.9 2.6 2.4 43000 -56.6 183.7 8.1 6.8 5.7 4.9 4.3 3.8 3.4 3.1 2.8 2.5 2.3 44000 -56.7 175.7 7.8 6.5 5.5 4.7 4.1 3.6 3.3 2.9 2.7 2.4 2.2 45000 -56.9 167.7 7.4 6.2 5.2 4.5 3.9 3.5 3.1 2.8 2.5 2.3 2.1 46000 -57.1 159.6 7.1 5.9 5.0 4.3 3.8 3.3 3.0 2.7 2.4 2.2 2.0 47000 -57.3 151.6 6.7 5.6 4.7 4.1 3.6 3.2 2.8 2.5 2.3 2.1 1.9 48000 -57.5 143.7 6.4 5.3 4.5 3.9 3.4 3.0 2.7 2.4 2.2 2.0 1.8 49000 -57.6 136.0 6.0 5.0 4.3 3.7 3.2 2.8 2.5 2.3 2.1 1.9 1.7 50000 -57.8 128.6 5.7 4.8 4.0 3.5 3.0 2.7 2.4 2.2 2.0 1.8 1.6