Grisms Developed for FOCAS
Abstract
Faint Object Camera and Spectrograph (FOCAS) is a versatile common-use optical instrument for the 8.2 m Subaru Telescope, offering imaging and spectroscopic observations. FOCAS employs grisms with resolving powers ranging from 280 to 8200 as dispersive optical elements. A grism is a direct-vision grating composed of a transmission grating and prism(s). FOCAS has five grisms with replica surface-relief gratings including an echelle-type grism, and eight grisms with volume-phase holographic (VPH) gratings. The size of these grisms is 110 mm × 106 mm in aperture with a maximum thickness of 110 mm. We employ not only the dichromated gelatin, but also the hologram resin as a recording material for VPH gratings. We discuss the performance of these FOCAS grisms measured in the laboratory, and verify it by test observations, and show examples of astronomical spectroscopic observations.
- Publication:
-
Publications of the Astronomical Society of Japan
- Pub Date:
- March 2011
- DOI:
- 10.1093/pasj/63.sp2.S613
- arXiv:
- arXiv:1105.0997
- Bibcode:
- 2011PASJ...63S.613E
- Keywords:
-
- faint object;
- instrumentation: high dispersion grism;
- techniques: high diffraction efficiency;
- Astrophysics - Instrumentation and Methods for Astrophysics
- E-Print:
- 18 pages, 12 figures, accepted for publication in PASJ 63, SP2 (Subaru special issue)