First light from the Dome C (Antarctica) of a phase knife stellar coronagraph

TL;DR

This paper presents the first daytime on-sky results of a phase knife stellar coronagraph operated in Antarctica, demonstrating promising performance under challenging conditions and providing insights for future improvements.

Contribution

First on-sky daytime results of a phase knife stellar coronagraph at Dome C, comparing laboratory and numerical models with real observations in Antarctica.

Findings

Total rejection exceeding 15 in the visible spectrum.

Coronagraphic performance achieved without correction systems.

Insights for optimizing future nighttime observations.

Abstract

We report on the first daytime on-sky results of a Phase Knife stellar Coronagraph operated in the visible from the French-Italian Concordia station at Dome C of Antarctica. This site has proven in the last few years to offer excellent atmospheric seeing conditions for high spatial resolution observations. The coronagraphic performances obtained from laboratory experiments and numerical models have been compared with those measured from daytime on-sky data recorded on bright single and multiple stars: Canopus (HD 45348), and alpha Centauri (HD 128620J). No correction system was used (adaptive optics or tip-tilt mirror) so that atmospheric turbulence alone defines the image quality, and thus the coronagraphic performances. Moreover, the experiment could not run under optimal operational conditions due to hardware/software problems. Satisfactory results have been obtained: broad band total rejection exceeding 15 were attained in the visible. This first day-time observation campaign yields an experimental feedback on how to improve the instrument to get optimal performances during future night-time observation runs.