The INT and JKT have a restricted set of ``core'' instruments, which should cover the requirements of a large fraction of users. The number of instrument changes on these telescopes is kept to a minimum to reduce costs and increase reliability. However, the design of the WHT allows much greater flexibility, since it is straightforward to switch between Cassegrain and the two Nasmyth focal stations. A much greater variety of instruments may therefore be left on the telescope. A broad functional division between the WHT, INT and JKT as regards common-user instruments is given in Table .
Table: Functional division of telescopes
Table summarises the instruments and detectors offered as common user instruments as of mid-1994.
Table: Instruments available
The rest of this manual describes these instruments in more detail. Instruments which perform a similar function are grouped together, to help potential observers decide which is the optimum instrument for their application. Chapter 4 describes the imaging instruments, whilst Chapter 5 describes the instruments available for spectroscopic observations. The various detectors available are described in Chapter 6. Chapter 7 describes the instruments for photometry and polarimetry. Details of the support for users' own instruments are given in Chapter 8.