Demonstration of an imaging technique for the measurement of PSF elongation caused by Atmospheric Dispersion

Elongation of the point spread function due to atmospheric dispersion becomes a severe problem for high resolution imaging instruments, if an corrector is not present. In this work we report on novel technique measure elongation, corrected or uncorrected, from data. By employing simple diffraction mask it possible magnify chromatic elongation caused by atmosphere and thus make easier measure. We discuss theory design such two proof concept observations using 40 cm Gratama telescope at University Groningen. evaluate acquired images geometric approach, forward modelling approach direct measurement length function. For first methods measurements consistent with models within 0.5 arcsec. Direct do prove suitable characterisation dispersion. conclude that addition type can be valuable PSF elongation. This enable precision correction future instruments.