The star photometer at AWIPEV is a permanent installation and fills the measurement gap of the sun photometer during polar night by using the brightness of defined stars. The instrument data is only available in clear sky conditions. In this regard the data should represent the real aerosol conditions. Only aerosols that are advected and processed within clouds or hygroscopic growth cannot be measured by this instrument. To minimize measuring errors bright and, as a local advantage, circumpolar stars are chosen for photometry. The three stars gamma Gem, beta UMa and alpha Lyr are used for both types of measurement. The star alpha Aql has only been used for two star measurement yet.
The measuring principle of a star photometer is the same as for the sun. There are two different possibilities to determine the AOD (aerosol optical depth) using a star photometer. One star measurement requires a calibration at very clear nights, just like Langley calibration for sun photometers. For the two star measurement a calibration is not needed in advance. But on the other hand the second method is much more effective by atmospheric inhomogeneities and horizontally stratified layers.
In this data set AOD, Angstrom-Exponent and modified Angstrom-Exponent (Graßl, Ritter 2019, Remote Sensing, https://doi.org/10.3390/rs11111362) are given for the star photometer at AWIPEV for the time 10 Nov. 2010 to 21. Feb 2021. The variables are in netcdf format for each measurement day. The used instrument for the entire measurment period was star04.
