An all-sky camera is a camera with a fish-eye lens that stares at the sky 24 hours a day. Why? Because getting up off the couch and walking outside to see what the sky looks like is WAY too much effort!
Actually, there are several reasons many observatories have all-sky cameras. One is to be able to see what the sky looks like to determine if observing is possible - but not due to laziness. When walking outside to look at the sky, your eyes take up to 30 minutes to become fully dark-adapted, which makes it hard to see things like wispy clouds that will interfere with observing or astrophotography. An all-sky camera is very sensitive and can see those clouds at any time.
Additionally, an all-sky camera can be set up to provide images on the internet, so the sky conditions can be monitored remotely, from a smart phone or web browser on a computer. And finally, the all-sky camera can be set up to record timelapse movies of the sky, allowing one to look back in time to see astronomical events such as an eclipse or a large meteor going across the sky.
A serious all-sky camera setup with weatherproof housing and capable software can run as much as $800 or more. Being the cheap person that I am, I went for a sensitive security camera that is designed to work by starlight. I wasn't sure if it would be good enough, but for $85, it seemed worth the risk. It's not as sensitive as a serisous all-sky camera, but it's good enough to do the job as a poor-man's all-sky camera.
For an up-to-date view of the current sky conditions at the observatory, including the all-sky camera image, use the Conditions link at the top of this page. For more details on the camera itself and the installation, use the Equipment link. Below, I've posted a couple of time lapse videos taken using the camera.