and Goody, 1992). The limiting magnitude depends on the atmospheric seeing, the spectral bandpass, the angular resolution to be achieved, and the quantum efficiency of the detector (Dainty and Greenaway, 1979). We reach with the TBL and detectors such as the CP40 and the PAPA with a bandpass of 70 nm. Without filters, the expected limiting magnitude would increase to about . In that case, the wavelength range is determined by the product of the sensitivity response of the detector with that of the photo-cathode, and the resulting bandwidth is a few hundreds of nanometers. It was shown both experimentally (Hege [*et al.*]{}, 1981) and with numerical simulations (Ziad [*et al.*]{}, 1994) that such extreme observing conditions can be used for faint detection of object duplicity.

[*5.2. Data processing and image restoration*]{}

10000 Whereas data quality is of paramount importance and obviously limits the angular resolution that can be ultimately obtained in the reconstructed images, the nature of the data reduction methods subsequently employed to extract the scientific information contained in these images plays a key role in ensuring the overall success of the scientific programs.

We have written the software to process data from the various detectors used (cf. 