For meteorological purposes, the objective of a sky camera is to record the cloud patterns in the sky. This is usually takes the form of a snapshot at a particular time, often the time of a weather observation, or as a time-lapse movie that allow the view to determine what is happening in the sky based on the type of clouds, the amount of the clouds and the direction the clouds are movie over a period of time.
All that is required to capture a sky image is a camera pointing towards the sky. However, even that is not as simple as it seems. The lens on the camera determines the amount of the sky that the camera can possibly capture. Telephoto lens provide a more detailed picture of less of the sky, while wide-angle lens provide a view of more of the sky, but with less detail about any particular area of the sky.
It is possible to get a fish-eye lens that can capture all of the sky, but most camera will be damaged if the Sun is in the field of view for any length of time. The other problem is the camera has to be suitable for operation during both the day and the night.
The commonly available security camera usually has a wide-angle lens and is capable of daytime operation using ambient light and night-time operation using infra-red, often supplied by the camera. Although the camera LEDs can light the foreground for a bit of perspective, in the city the most important illumination at nights is the Infra-Red radiation given off by the city as the low clouds will reflect enough radiation to be visible to the camera.
All that is required to capture a sky image is a camera pointing towards the sky. However, even that is not as simple as it seems. The lens on the camera determines the amount of the sky that the camera can possibly capture. Telephoto lens provide a more detailed picture of less of the sky, while wide-angle lens provide a view of more of the sky, but with less detail about any particular area of the sky.
It is possible to get a fish-eye lens that can capture all of the sky, but most camera will be damaged if the Sun is in the field of view for any length of time. The other problem is the camera has to be suitable for operation during both the day and the night.
The commonly available security camera usually has a wide-angle lens and is capable of daytime operation using ambient light and night-time operation using infra-red, often supplied by the camera. Although the camera LEDs can light the foreground for a bit of perspective, in the city the most important illumination at nights is the Infra-Red radiation given off by the city as the low clouds will reflect enough radiation to be visible to the camera.
