2007/02/27 by Justin Crepp, Justin R. Crepp, Andrew D. Vanden Heuvel +2
Engineering · Physics and Astronomy · #Adaptive optics and wavefront sensing #Optical Polarization and Ellipsometry #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/516773
Accepted to ApJ
arxiv created 2007/02/27 · openalex publication_date 2007/05/29 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
As adaptive optics technology continues to improve, the stellar coronagraph will play an ever increasing role in ground-based high-contrast imaging observations. Although several different image masks exist for the most common type of coronagraph, the Lyot coronagraph, it is not yet clear what level of wave front correction must be reached in order to gain, either in starlight suppression or observing efficiency, by implementing a more sophisticated design. In this paper, we model image plane Lyot-style coronagraphs and test their response to a range of wave front correction levels, in order to identify regimes of atmospheric compensation where the use of hard-edge, Gaussian, and band-limited image masks becomes observationally advantageous. To delineate performances, we calculate the speckle noise floor mean intensity. We find that apodized masks provide little improvement over hard-edge masks until on-sky Strehl ratios exceed ~0.88 S qs , where S qs is the intrinsic Strehl ratio provided by the optical system. Above this value, fourth-order band-limited masks outperform Gaussian masks by generating comparable contrast with higher Lyot stop throughput. Below this level of correction, hard-edge masks may be preferentially chosen, since they are less susceptible to low-order aberration content. The use of higher order band-limited masks is relegated to situations where quasi-static residual starlight cannot be sufficiently removed from the search area with speckle-nulling hardware.