Daytime Sky Quality at El Leoncito, Argentina

F. A. IGLESIAS; C. FRANCILE; LAZARTE-GELMETTI, J; L. A. BALMACEDA; H. CREMADES; F. CISTERNA

San Juan

Conferencia; 65va Reunión Anual de la AAA; 2023

Asociación Argentina de Astronomía

We characterize the daytime sky quality in terms of brightness, cloud coverage, and main weather variables at the Carlos Ulrico Cesco station of the Felix Aguilar Astronomical Observatory (OAFA), located in ElLeoncito National Park, San Juan, Argentina. We collect more than 15 years of daily observations fromthe auxiliary sky brightness detectors of the Mirror Coronagraph for Argentina (MICA, operative from 1997 to2012), including daily observing reports. We additionally present data from two meteorological stations operatedat the site from 2000 to 2020. We determine the main statistical properties and seasonal variability of daytimesky brightness, clear sky time fraction (CSTF), precipitable water vapor (WV), temperature, humidity, and windspeed, which are relevant for solar, particularly coronal observations. Our results confirm that El Leoncito isan excellent place to perform daytime astronomical observations. We measure a median sky brightness of 15.8ppm, estimated at 526.0 ± 1.0 nm and 6 Rs from the solar disk center; a median CSTF of 0.7; anda median WV below 6 mm. These values, and those of other relevant weather variables, are comparable tothe levels found among the best astronomical observing sites in the world. Due to the extended period of timeanalyzed and high sampling frequency, the novel data and results presented in this report contribute to theanalysis and interpretation of historical sky brightness data and are of great value for the future planning ofdaytime astronomical instrumentation at El Leoncito. For further details see Iglesias et. al. (2023).