Optimized MASS device for synchronous measurements with Paranal DIMM. ... System 1.2.2 Fabry lens . ... 3.2 Device alignments at the telescop 3.2.1 Fabry lens p osition . ... Optical layout of MASS device in ZY plane . Optical layout of the MASS device in ZX plane MASS segmentator . ... Other values are explained in text. working entrance pupils for the MASS devices can b e defined in reverse light path as the images of these pupil stops pro duced by the Fabry lens + telescop e optical system. ...