  We present here results from large zenith-angle observations with the CAT
atmospheric Cherenkov imaging telescope, based on data taken on the Crab Nebula
and on the blazar Mk501 from 1996 onwards. From Monte Carlo simulations, the
threshold energy of the telescope is expected to vary from about 250 GeV at
zenith to about 2 TeV at a zenith angle of 60 degrees. The lower source-fluxes
due to the increased threshold energy are partly compensated for by an increase
in the effective collection area at large zenith angles, thus allowing a
significant extension of the dynamic range of the CAT telescope, with a
tolerable loss in sensitivity. We discuss the implications for source detection
and energy spectrum measurements.
