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STIS has a single coronagraphic mask aperture for direct imaging. The aperture (50CORON) contains one occulting bar and two intersecting wedges. The wedges vary in width from 0.5 to 3.0 arcseconds over their 50 arcseconds length, while the rectangular bar measures 10 by 3 arcseconds. A small occulting finger located on the right-hand side of the detector (BAR5) was damaged during assembly of STIS and was not used until Cycle 25, when it’s performance was tested. Now, the STIS team recommends using BAR5 as a fully-supported capability for coronagraphic science. BAR5, alongside the rounded corners of BAR10, provides STIS users with a flexible instrument for low inner working angle coronagraphy. See STIS ISR 2017-03 for more details.

Design of the STIS Coronagraphic Mask
Design of the STIS Coronagraphic Mask


Last Updated: 06/02/2023


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