A Charge Coupled Device (CCD) is a 2-dimensional electronic image detector.
Its enormous attractions for astronomers are threefold: linearity, with
dynamic ranges of 10000 being realized; speed, with quantum efficiencies
of up to 80 per cent; and wavelength response, some devices being usable
from the near UV (< 300 nm) to the near IR (> 1 
m).
CCDs offer a considerably smaller area than photographic plates, but the improved performance generally outweighs this disadvantage. CCDs suffer from readout noise, which makes them less suitable than an IPCS at very low count rates, in particular while observing faint objects at high dispersion with the UES. CCDs integrate signal during the exposure, and then exhibit a finite read-out time afterwards- this can be many 10s of seconds for the large arrays; in contrast the IPCS has a real-time data collection.
CCDs are used on La Palma for both spectroscopic and imaging observations. This section is a brief description of these detectors. Some useful references for further reading are:
McLean, I.S. 1989. Ellis Horwood.
*
Electronic and computer-aided astronomy.
*
*
ESO-OHP workshop on the Optimization of the Use of CCD
detectors in astronomy.
*
Editors: Baluteau, J.P. & D'Odorico, S., 1986
*
*
Wall, J.V. & Laing, R.A.
*
User's Guide to the prime focus CCD camera on the INT
*
*
Argyle, R.W., Mayer, C.J., Pike, C.D. & Jorden, P.R.
*
User Guide to the JKT CCD camera, 1988.
*
*
Jorden, P.R. & Lupton, W.L.
*
Spectroscopy with the CCD on the INT, 1984.
*
*
Jorden, P.R. Basic parameters of CCDs in use at La Palma,
*
La Palma Technical Note 55, latest version Nov 1990
*
*
Jorden, P.R. CCD Frame size parameters
*
ING La Palma Technical Note 79, Dec 1990
*
Oates, A.P., & Jorden, P.R. New Large-Format CCDs for the ING
*
ING La Palma Technical Note 92, Nov 1993
*
Jorden, P.R. Properties of Operational Cameras
*
ING La Palma Technical Note 93, Jan 1994