First light: May 2002.
De-commissioned: 31 January 2015.
Designed and built by: Optical Science Laboratory of the University College London (UCL).
Description: OSCA is the coronographic mask device to be used in combination with NAOMI and INGRID for infrared coronography. OSCA effectively suppresses light of a bright object and therefore enables the detection of faint structures or objects close to the host object which are otherwise overshined. OSCA is mounted permanently after the AO system NAOMI at the WHT and can be deployed within a few seconds into the beam making the system very flexible during nighttime. Six different mask sizes with hard edges are permanently mounted inside OSCA: 0"2, 0"65, 0"8, 1"0, 1"6 and 2"0. Two gaussian shaped masks with fwhm=0"5 and 0"6 optimized for the optical wavelength domain are also available. All masks can be selected remotely.