Photometry-Free Sky Area Visibility Estimation Method for All-sky Camera

Observatories typically deploy all-sky cameras for monitoring cloud cover and weather conditions. However, many of these cameras lack scientific-grade sensors, resulting in limited photometric precision, which makes calculating the sky area visibility distribution via extinction measurement challenging. To address this issue, we propose a Photometry-Free Sky Area Visibility Estimation method (PFSAVE). This method uses the standard magnitude of the faintest star observed within a given sky area to estimate visibility. By employing a per-transformation re-fitting optimization strategy, we achieve a high-precision coordinate transformation model with an accuracy of 0.42 pixels. Based on the results of \textSource Extractor, we propose screening criteria to reduce false detections. HEALPix segmentation is introduced to achieve high spatial resolution. Comprehensive analysis based on real all-sky images demonstrates that our method exhibits higher accuracy than the extinction-based method. Our method can support both manual and robotic dynamic scheduling, especially in partially cloudy conditions.