cm at the 3.6 m CFH or ESO telescopes.

The SCIDAR (SCintillation Detection And Ranging) technique (Vernin & Roddier, 1973) which consists in analysing the images of the pupil brightness lit by two stars to measure the wind speed and the altitude of the turbulence layers, could also be applied with PISCO. In that case, fast detectors operating at frequencies larger than 200 Hz (such as the PAPA or the RANICON cameras, cf. §4) are needed to “freeze” the turbulence.

[**4. The detectors**]{}

10000 PISCO has been used with a wide range of detectors. Actually, the qualities of the detector mainly condition the performances of the image restoration process. A good knowledge of the limitations of the detector is essential to elaborate a strategy of observation and obtain valid measurements. Here we describe the detectors that we have already tested on PISCO. For a wider information about the detectors used in the field of optical speckle interferometry, see for instance a review in Cuby (1988), Richard [*et al.*]{}, (1990) or Cuby [*et al.*]{}, (1990).

[*4.1. The CP40-INSU detector*]{}

10000 The first CP40 detector was designed at CERGA for interferometry observations by A. Blazit (Blazit, 1976, 1987). It is a two-stage 