Basic camera design
The three cameras are based upon a four element double Gauss type lens, with two glass types per camera to keep the cost within bounds. The performance of the cameras is quite typical of their type.
The glass thickness has had to be kept to a minimum, particularly within the u’ camera, to keep the throughput as high as possible.
The cameras were optimised for an infinite object distance with a field angle dictated by the required field size on the WHT and the need for the telescope pupil to be re-imaged onto the camera ‘stop’ by the collimator at sufficient distance from the last surface of the collimator that the dichroics could be placed between collimator and camera.
Filters are placed between the last surface of the camera lens and the window into the evacuated enclosure of the CCD.