Measurement of the atmospheric primary aberrations by a 4-aperture differential imagemotion monitor

Abstract

The present paper investigates and discusses the ability of the Hartmann test with a4-aperture differential image motion monitor (DIMM) to measure the atmospheric primaryaberrations which, in turn, can be used for the calculation of the atmospheric coherencetime. Through performing numerical simulations, we show that the 4-aperture DIMM isable to measure the defocus and astigmatism terms correctly whereas its results are notreliable for the coma. The most important limitations in the measurement of the primaryaberrations by the 4-aperture DIMM are the centroid displacements of the spots which arecaused by the higher order aberrations. This effect is negligible in the calculation of thedefocus and astigmatisms, whereas it cannot be ignored in the calculation of the coma.