Anisoplanatism across wide fields at high-frame rates

Abstract

ABSTRACT In this paper we present a preliminary analysis of variation in the isoplanatic patch size over short timescales andwide angular separations. We tested a visible band photon counting camera running with four 1 K 2 detectorsto provide a contiguous “eld of view of 1000 × 4000 pixels. Resolution was 35 100 mas per pixel at frame ratesfrom 20 111hz, providing data on atmospheric turbulence at angular separations of up to 400 arcseconds. Wediscuss the potential of such cameras to perform high resolution optical surveys using developments of standardlucky imaging techniques, and the implications of our results for adaptive optics systems design.Keywords: instrumentation: high angular resolution „methods: data analysis „ techniques: high angularresolution „ techniques: image processing 1. INTRODUCTION Anisoplanatism is a familiar eect in the “eld of ground based high resolution astronomical imaging. Dieringlight propagation paths for stars of angular separation larger than a few arcseconds result in dierent turbulentwavefront perturbations. As a result correcting for these turbulent perturbations, or selecting moments whenthey are of lesser severity, with regard to a reference star will produce a point spread function (PSF) that variesover the “eld of view.Considerable eort has been made to characterise the variation of the PSF in adaptive optics (AO) imageswith the aim of improving data analysis techniques, and progress is also being made in wide “eld AO designs suchas multi-conjugate AO.