to 35 °C, with variations smaller than the 10% systematic uncertainty stated by the manufacturer.

When SQMs are installed permanently outdoors for long-term monitoring, their sensitivity can degrade over time due to environmental exposure. A 2021 study demonstrated that this ageing effect - caused by factors such as reduced sensor sensitivity and optical degradation - can lead to systematic darkening of measurements. The researchers proposed a correction method using twilight sky brightness as a natural calibration source. By comparing