A Coronagraph with a Variable‐Diameter Occulting Disk

In order to optimize the occulting process of a classical Lyot coronagraph for imaging faint satellites next to Jovian planets, we designed a coronagraph with a variable-diameter occulting disk (Hg mask). We present the description of the Hg-mask coronagraph developed at the Observatorio Nacional, Rio de Janeiro, and the imaging test on Neptune's satellite Proteus.