1 Introduction

Very large telescopes are needed for imaging stellar disks or exo-planets but it will be difficult to expand the size beyond that of current "Extremely Large Telescope'' projects such as the 30 m CELT and the 100 m OWL (Gilmozzi et al. 1998), for technological and cost reasons. Interferometry can provide various trade-offs between angular resolution and collecting area, but snapshot imaging is often desirable to observe short-lived phenomena. In 1996, Labeyrie (1996) described the possibility of making snapshot images with multi-aperture interferometers, using a densified pupil. This optical architecture allows direct high-resolution imaging with high contrast. A miniature instrument, using a diffractive approach to pupil densification, has been successfully tested by Pedretti et al. (2000) on bright binary stars. Now, we present results similarly obtained with an improved optical scheme for achieving the pupil densification. In Sects. 2 and 3 we describe the principle of hypertelescopes and the experimental setup. Section 4 presents the results obtained on the sky. And finally, the optical schemes are further discussed in Sect. 5.