Hello,
I found the solar position model used in gensky, which calculates solar azimuth and altitude based on solar declination angle, in the IES handbook. However, I’m curious about the source of the solar adjustment factor in calculation of solar time equation used in the model as a picture of source code below. Does anyone have information on this?
warm regards,
Inwoo
I thought this formula also originated from the IES Lighting Handbook, but it would have been from a late 1980’s edition. By appearance, it looks like an imperfect compensation for the Earth’s elliptical orbit and precession, but I am only guessing.
The more accurate calculation accessed with the new gensky and gendaylit -y options derive from the Michalsky algorithm from 1988, cited at the top of ray/src/gen/sun.c. This is also implemented in ray/src/cal/cal/sun2.cal if you want to use it with icalc or rcalc.
Best,
-Greg