Refraction correction algorithms

Methods of calculating the effect of atmospheric refraction on solar elevation. Some methods account for secondary effects from temperature and pressure.

refraction.archer(elevation)	Atmospheric refraction correction based on the Archer algorithm.
refraction.bennett(elevation[, pressure, ...])	Atmospheric refraction correction based on the Bennett algorithm.
refraction.hughes(elevation[, pressure, ...])	Atmospheric refraction correction based on the Hughes algorithm.
refraction.michalsky(elevation)	Atmospheric refraction correction based on the Michalsky algorithm.
refraction.sg2(elevation[, pressure, ...])	Atmospheric refraction correction based on the algorithm in SG2.
refraction.spa(elevation[, pressure, ...])	Atmospheric refraction correction from the SPA algorithm.