sunset, and dusk, by Greg Pelletier, translated from NOAA's online calculators for solar position and sunrise/sunset An Excel workbook with a solar position and solar radiation time-series calculator, by Greg Pelletier Sun Position Calculator Free on-line tool to estimate the position of the sun with three different algorithms. PVCDROM Azimuth Angle - online material regarding Photovoltaics by UNSW, ASU, NSF et al. Horizontal coordinate system Sun Solar energy