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The NASA Dawn spacecraft acquired thousands of images of asteroid Vestaduring its year-long orbital tour, and is now on its way to asteroid Ceres. Amethod for calibrating images acquired by the onboard Framing Camera wasdescribed by Schr\"oder et al. (2013; Icarus 226, 1304). However, their methodis only valid for point sources. In this paper we extend the calibration toimages of extended sources like Vesta. For this, we devise a first-ordercorrection for in-field stray light, which is known to plague images takenthrough the narrow band filters, and revise the flat fields that were acquiredin an integrating sphere before launch. We used calibrated images of the Vestasurface to construct simple photometric models for all filters, that allow usto study how the spectrum changes with increasing phase angle (phasereddening). In combination with these models, our calibration method can beused to create near-seamless mosaics that are radiometrically accurate to a fewpercent. Such mosaics are provided in JVesta, the Vesta version of the JMARSgeographic information system.

In-flight calibration of the Dawn Framing Camera II: Flat fields and stray light correction