Allsky

Allsky refers to all-sky imaging systems that capture the entire sky above a location in a single frame. These systems typically use a fisheye lens to achieve a wide field of view and a digital sensor such as a CCD or CMOS detector. Modern all-sky cameras often operate autonomously, recording time-lapse sequences or stills and transmitting data to a central server for processing. They are commonly housed in weatherproof enclosures and configured for continuous operation.

Principles and components: A fisheye or ultra-wide lens provides coverage close to a full hemisphere. The sensor captures light from the entire sky, usually in color but sometimes in monochrome for increased sensitivity. Exposure times range from a fraction of a second to several seconds, depending on lighting conditions. Software analyzes the images to identify stars, meteors, clouds, and other phenomena, and may generate cloud masks or weather reports. Some systems include infrared sensitivity to better observe under moonlight or hazy conditions.

Applications: All-sky cameras are used for meteor observation and the study of meteor showers, as well as for aurora monitoring in polar regions. They provide essential cloud-cover data for astronomical observations and telescope scheduling, and are frequently employed in education and public outreach to show live sky conditions. Many projects operate networks of all-sky cameras to compile long-term sky surveys and weather context.

Variations and data: Deployments range from single-unit setups for amateurs to networks run by research institutions. Data outputs typically include time-lapse imagery, meteor detections, cloud masks, and sky-condition reports, which can be integrated with other astronomical or meteorological datasets.

Limitations: Resolution is constrained by sensor size and optics, and performance is affected by light pollution and atmospheric conditions. All-sky cameras are not intended for precise photometry but provide valuable context and event detection for observational campaigns.