Colorimetric and Spectroradiometric Characteristics of Narrow-Field-of-View Clear Skylight in Granada, Spain
Abstract
As part of our ongoing research into the clear daytime sky's visible structure, we analyze over 1500 skylight spectra measured during a seven-month period in Granada, Spain. We use spectral radiances measured within 3 deg fields of view (FOV's) to define colorimetric characteristics along four sky meridians: the solar meridian and three meridians at azimuths of 45 deg, 90 deg, and 315 deg relative to it. The resulting clear-sky chromaticities in 44 different view directions (1) are close to but do not coincide with the CIE daylight locus, (2) form V-shaped meridional chromaticity curves along it (as expected from theory), and (3) have correlated color temperatures (CCT's) ranging from 3800 K to infinity K. We also routinely observe that sky color and luminance are asymmetric about the solar meridian, usually perceptibly so. A principal-components analysis shows that three vectors are required for accurate clear-sky colorimetry, whereas six are needed for spectral analyses.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 2001
- Accession Number
- ADA526046
Entities
People
- Javier Hernandez-andres
- Javier Romero
- Raymond L. Lee Jr.
Organizations
- University of Granada