Bennett returns refraction for obtaining true altitude.

Bennett2 returns refraction for obtaining true altitude.

Gt15Apparent returns refraction for obtaining apparent altitude when altitude is greater than 15 degrees (about .26 radians.) h must be a computed true "airless" altitude of a celestial body.

Gt15True returns refraction for obtaining true altitude when altitude is greater than 15 degrees (about .26 radians.) h0 must be a measured apparent altitude of a celestial body.

Saemundsson returns refraction for obtaining apparent altitude.