Vol. 8, issue 03, article # 2

Abstract:

Ground and low–altitude layers perturbing the incoming wave front are characterized by a very high field–of–view isoplanatism. However, images of a sodium beacon and stars are affected also by high–altitude layers, characterized by a small isoplanatic angle. Correction of an off–axis image of an object using the latter type of reference wave will introduce an additional degradation of the wave front due to the lack of correlation between the high–altitude layers seen at different angles, while the use of small altitude Rayleigh reference source is affected only by the loss of information on the higher layers. A trade–off between the two approaches, versus the covered field of view, and the C²_n(z) behavior is discussed in this paper.