Sky brightness evaluation and first coronal signal detection from Concordia Base (Antarctica) with a calibrated micropolarizer array camera

The solar corona is the outer layer of the Sun atmosphere. The brightness of the solar corona is a million times lower than the solar disk. The Earth’s sky brightness itself is higher enough to cover the coronal signal during ground-based observations. For this reason, the study of sky characteristics plays a fundamental role in observing the solar corona. To date, the only place with the sky characteristics that allow continuous coronagraphic measurements from Earth is at the MLO (Mauna Loa Observatory; Hawaii, ≈ 3400 m a.s.l.). This paper shows the results obtained as part of the “Extreme Solar Coronagraphy Antarctic Program Experiment” (ESCAPE) at Concordia Base, Antarctica (Dome C plateau-coord: 75 06S; 123 20E-≈ 3300 m above sea level) during the 37th campaign and give a summary of all the sky-brightness measurements obtained from this site (campaign 34th and 35th). Dome C is confirmed to be a coronagraphic site with a sky brightness value of about 1×10^−6 B⊙. For the first time, it was also possible to detect a coronal signal and to compare it with what was measured by the COronal Solar Magnetism Observatory (COSMO) K-coronagraph (K-Cor) at the MLO. All these results were obtained by using a micropolarizer camera mounted within a coronagraph designed for Antarctic environments.