Xie, H. W., Zhi, H., Kang, Z., et al. 2025. Photometry-free sky area visibility estimation method for All-sky Camera. Astronomical Techniques and Instruments, 2(1): 52−64. https://doi.org/10.61977/ati2024056.
Haiwen Xie1, 2, Hui Zhi3, Zhe Kang1, , Shiyu Deng1, 3, Bingli Niu4, Lei Wang2, 3, Xiaojun Jiang2, 3
- Changchun Observatory, National Astronomical Observatories, Chinese Academy of Sciences, Changchun 130117, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- CAS Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China
- Nanjing Institute of Astronomical Optics & Technology, Chinese Academy of Sciences, Nanjing 210042, China
Abstract
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 the Photometry-Free Sky Area Visibility Estimation (PFSAVE) method. 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. Using the results of , we propose screening criteria to reduce false detections. HEALPix segmentation is also 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 supports both manual and robotic dynamic scheduling, especially under partially cloudy conditions.
Keywords
All-sky cameras, Astronomy image processing, Ground-based astronomy, Calibration, Computational methods, Observational astronomy