We describe a method to calibrate the elements of a multispectral imaging system aimed at skylight imaging, which consists of a monochrome charge-coupled device (CCD) camera and a liquid crystal tunable filter. We demonstrate how to calibrate these two devices in order to build a multispectral camera that can obtain spectroradiometric measurements of skylight. Spectral characterizations of the tunable filter and the camera are presented together with a complete study of correcting temporal and spatial noise, which is of key importance in CCDs. We describe all the necessary steps to undertake this work and all the additional instrumentation that must be used to calibrate the radiometric devices correctly. We show how this complete study of our multispectral system allows us to use it as an accurate, high resolution spectroradiometer.