Closed
Description
Describe the bug
Low sun angles with a tilted tracking axis cause an error in the backtracking calculation. Code attempts arcos() of a value outside [-1, 1]
To Reproduce
from pvlib.tracking import singleaxis
result = singleaxis(apparent_zenith=80, apparent_azimuth=338, axis_tilt=30,
axis_azimuth=180, max_angle=60, backtrack=True, gcr=0.35)
Expected behavior
tracker angle should set to max_angle
Versions:
pvlib.__version__: 0.6.1pandas.__version__: 0.23.3- python: 3.6