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Hg-Mask Coronagraph

Published online by Cambridge University Press:  29 August 2011

C. Aime ,
R. Soummer ,
P. Bourget ,
C. H. Veiga ,
R. Vieira Martins ,
P. Assus  and
F. Colas
P. Bourget
Affiliation:
Observatório Nacional - Rio de Janeiro, Brazil
C. H. Veiga
Affiliation:
Observatório Nacional - Rio de Janeiro, Brazil
R. Vieira Martins
Affiliation:
Observatório Nacional - Rio de Janeiro, Brazil
P. Assus
Affiliation:
OCA - Nice, France
F. Colas
Affiliation:
IMCCE - Paris, France
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Abstract

In order to optimize the occulting process of a Lyot coronagraph and to provide a high dynamic range imaging, a new kind of occulting disk has been developed at the National Observatory ofRio de Janeiro. A mercury (Hg) drop glued onto an optical window by molecular cohesion and compressed by a pellicle film is used as the occulting disk. The minimum of the superficial tension potential function provides an optical precision (lambda/100) of the toric free surface of the mercury. This process provides a size control for the adaptation to the seeing conditions and to the apparent diameter of a resolved object, and in the case of adaptive optics, to the Airy diameter fraction needed. The occultation is a three dimensional process near the focal plane on the toric free surface that provides an apodization of the occultation. The Hg-Mask coronagraph has been projected for astrometric observations of faint satellites near to Jovian planets and works since 2000 at the 1.6 m telescope of the Pico dos Dias Observatory (OPD - Brazil).

Type
Research Article
Information
European Astronomical Society Publications Series , Volume 12: Astronomy with High Contrast Imaging II , 2004 , pp. 205 - 211
Copyright
© EAS, EDP Sciences, 2004

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