The following table gives atmospheric refraction corrections to derive the apparent altitude of a celestial object above the horizon given the observer's height above mean sea level and the unrefracted altitude of the object.

The corrections given here are based on atmosphreic height/temperature and height/pressure relations given by P.N. Tverskoi (ffphysics of the Atmosphere", [translated from Russian] pub.  Isreal Program for Scientific Translations for NASA and NSF, 1965, p.57). The atmospheric data taken from this source are reproduced below in the original units (km, degrees K, and mm) and in converted units (feet, degrees C, and millibars).


Temperature and Pressure of The Atmosphere (from Tverskoi, 1965)

	km	oK	mm	feet	oC	mbars

	0	294	757.0	0	21	1070.0
	2	278	598.0	6562	5	845.3
	4	261	466.0	13123	-12	658.7
	6	247	358.0	19685	-26	506.0
	8	233	270.0	26247	-40	381.6
	10	220	201.0	32808	-53	284.1
	12	217	149.0	39370	-56	210.6
	16	215	79.0	52493	-58	111.7
	20	216	41.9	65617	-57	59.2


The refraction correction table gives the correction, in minutes of arc, to be applied to the unrefracted altitude of the object, in degrees, given the observers height above MSL.  The table is tabulated for observer heights in the range of 0 to 50000 feet in 1000 foot increments, and object altitudes of 0 to 10 degrees in increments of 0.5 degrees.  Temperatures and pressures for the refraction model at each observer height were obtained by a cubical spline fit to the above table.  The direction of the corection is toward the zenith.




Glenn Schneider
Space Telescope Science Institute 3700 San Martin Drive
Johns Hopkins University
Homewood Campus
Baltimore, MD 21218