Nighttime measurements of atmospheric optical thickness by star photometry with a digital camera.
Nighttime stellar photometric measurements have been carried out with a commercial digital single-lens reflex camera to determine the atmospheric optical thickness on large fields of view (FOV). Specific procedures of image analysis allow to extract an equivalent irradiance for a number of stars and for the sky light background; thus, a measure of the optical thickness in each star direction can be retrieved. A larger FOV is obtained by stitching several photographs shot in quick sequence on adjacent regions of the sky: such measurements provide almost instantaneous maps of optical thickness and skylight background that indicate the degree of homogeneity of the aerosol load. Additional information provided by the combined use of the camera and a lidar is presented. The zenithal optical thickness is used with values of the aerosol backscatter provided by a lidar system to obtain the aerosol extinction-to-backscatter ratio.
Dipartimento di Fisica, Università di Roma "La Sapienza," Piazzale Aldo Moro 5, 00185 Roma, Italy. orietta.lanciano@gmail.com
Orietta
O
Lanciano
Giorgio
G
Fiocco