Introduction to atmospheric models (1/6)

Numerical models

When crossing the terrestrial atmosphere, a light particle - coming from a star, for example - undergoes numerous deviations, diffusions and absorptions, known as the atmospherical refraction and extinction phenomena. The effect of these phenomena is the impossibility of observing the theoretical rising and setting azimuths of a star. In fact, only its positions of appearance and disappearance on the surface of an artificial horizon whose height above the terrestrial horizon depends upon the visual magnitude of the considered object, the brightness of the background sky, the temperature and relative humidity of the ambient air, the visual accuity of the observer, can be sighted.

Because of the combination of the atmospheric refraction and extinction phenomena, can only be seen,
from earth, the appearance and disappearance positions of a star above an artificial horizon whose height
above the earth surface is related to the visual magnitude of the considered object, the brightness
of the background sky, the temperature and relative humidity of the ambient air, etc.

Contrarily to Steven C. Haack, we today have atmospheric models (20) at our disposal whose combination with the most recent theories of celestial mechanics (21) allows us to accurately determine the time, the height and the azimuth of appearance or disappearance of a star on the local vault. The validity of these models not only applies to dark sky, but also to twilight and daylight skies. In order to check everyone of the possible stellar hypothesis, let's therefore extend our study to dark and twilight skies. Let's determine everyone of the stars whose appearance and disappearance azimuths in the dark and twilight skies were close to the errors in alignment of the pyramids of Djoser, Huni, Snofru, Khufu, Djedefre, Khafre, Menkaure, Sahure, Neferirkare and Unas.