2025MNRAS.537..617Y

A high-precision calibration method for all-sky cameras has been realized using images from the Ali observatory in Tibet, providing application results for atmospheric extinction, night sky brightness, and known variable stars. This method achieves high-precision calibration for individual all-sky images, with the calibration process introducing deviations of less than 0.5 pixels. Within a 70-deg zenith angle, the calibration deviation of the images is less than 0.25 pixels. Beyond this angle, the calibration deviation increases significantly due to the sparser distribution of stars. Increasing the number of stars with zenith angles greater than 70 deg used for calibration can improve the calibration accuracy for areas beyond the 70-deg zenith angle, reducing the calibration deviation at an 85-deg zenith angle to 0.2 pixels. Analysis of the all-sky images indicates that the atmospheric extinction coefficient at the Ali Observatory is approximately 0.20, and the night sky background brightness is about 21 mag per square arcsec, suggesting the presence of urban light pollution.