Measuring Night Sky Quality
Our valley is in the process of applying for an IDA dark sky certification. In order to qualify, exact measurements of the night sky are necessary. A friend and I volunteered to conduct the actual measurements. Since we have a dusk-to-dawn curfew due to the pandemic, we needed a special permission for our nighttime adventure. Of course the measurements can only be done during the time of the so-called astronomical darkness (i.e., when the sun is 18° below the local horizon) and without any moonlight. For each spot we had to take six individual measurements that were then used to calculate the average for each spot. In addition, measurements had to be conducted at the presumed brightest location of the valley as well as at the darkest one. It took us a whole night (from 9pm until 5am) and 142 km with 25 individual locations to complete this task. Needless to say, the results were more than satisfying. Of course a one-time measurement is not enough. These tests have to be repeated at least once each season.