intensified CCD camera followed by a photon analyzer which computes the coordinates of the photo-events (Foy, 1988b). The field is covered by a mosaic of 4 CCD’s, 288$\times$384 pixels each. We actually used the duplication of this prototype, financed by INSU to make it available to the French astronomical community and in particular to the instruments of the TBL.

The exposure time is set to 20 msec, which may be too large for speckle applications when the coherence time is smaller than this value. To circumvent this difficulty a rotating shutter was implemented which reduces the exposure time to 5 or 10 msec. This shutter interrupts the light beam in the speckle camera with a rotating opaque sector synchronized with the frame signal of the CP40 (phase-locked motor).

Because of a dead zone between the 4 image quadrants of the CP40, we decided to use only one quadrant and made a special “off-axis” mechanical interface to align the center of the selected quadrant with the optical axis of PISCO.

The geometrical distortion caused by the two-stage amplifier is rather large, of the order of 20% in the edges (Thiebault, 1994).

Another problem is a strongly non-uniform sensitivity of the photo-cathode 