We climbed up Binsey in the dark. I was pleased that the long exposure on the camera was able to let in enough light to make any sort of picture. I put the camera on a tripod and used the timer to avoid knocking the camera because I'm guessing the shutter was open for several seconds. I need to come up with a strategy for measuring it. It is a time when the Charge Coupled Device CCD that is the light sensor comes into its own because it has a quantum efficiency of 70% compared to 4% for chemical films. That means that 70% of the photons are detected so they can operate in lower light intensities.
