Wide-field imaging at mid infrared wavelengths: reconstruction of chopped and nodded data

Abstract

Ground-based astronomical observations at thermal infrared wavelengths face the problem of extracting the weak astronomical signal from the large and rapidly variable background flux. The observing strategy most commonly used, the so-called ``chopping and nodding'' differential technique, provides reliable representations of the target uniquely in the case of compact sources while extended and complex sources can be easily distorted by their negative counterparts. A restoration method, designed to remove the negative values and to provide reliable representations of extended sources has been proposed. We show that the algorithm successfully removes the distortions due to the negative counterparts and, in addition, provides noise reduction.