2 research outputs found
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 atmospheric
dispersion corrector is not present. In this work we report on a novel
technique to measure this elongation, corrected or uncorrected, from imaging
data. By employing a simple diffraction mask it is possible to magnify the
chromatic elongation caused by the atmosphere and thus make it easier to
measure. We discuss the theory and design of such a mask and report on two
proof of concept observations using the 40 cm Gratama telescope at the
University of Groningen. We evaluate the acquired images using a geometric
approach, a forward modelling approach and from a direct measurement of the
length of the point spread function. For the first two methods we report
measurements consistent with atmospheric dispersion models to within 0.5
arcsec. Direct measurements of the elongation do not prove suitable for the
characterisation of atmospheric dispersion. We conclude that the addition of
this type of diffraction mask can be valuable for measurements of PSF
elongation. This can enable high precision correction of atmospheric dispersion
on future instruments.Comment: Accepted for publication in the Monthly Notices of the Royal
Astronomical Society. Contains 11 pages, 11 figures, 2 table