In any telescope you need two things; something to focus the light to an image and, a mechanism that records the resulting image. In an ordinary optical telescope the focussing can either be done by a properly shaped piece of glass (a lens) or by a parabolic mirror. The recording mechanism can be your eye, a sheet of photographic film or, like in modern digital cameras, an array of CCD (charge coupled device) pixels.
In an x-ray telescope both the lens and the the image detector present problems. Neither glass nor ordinary mirrors work because the x-rays go right through them. The answer is to use what is called a 'grazing incidence mirror'. The image detector is called a 'micro-channel plate'.
There is a nice description of the famous Chandra_X-ray telescope at:
LeeH
(published on 10/22/2007)
