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ING Newsletter No. 7, December 2003

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OASIS at the WHT

Chris Benn (ING), Gordon Talbot (ING), Roland Bacon (Univ. of Lyon)

T he optical integral-field spectrograph OASIS, formerly at the CFHT, has moved permanently to the WHT. It is now installed at one of the science ports of NAOMI, the WHT’s adaptive-optics system. OASIS was successfully commissioned on-sky with NAOMI in July 2003, and it is offered to the community on a shared-risks basis in semester 2004A.

Figure 1 Figure 2
Figure 1 (left). OASIS (left) joins NAOMI in the WHT’s new AO-dedicated, temperature-controlled Nasmyth enclosure, GRACE. The IR camera INGRID is visible in the foreground on the right [ JPEG | TIFF ]. Figure 2 (right). OASIS logo for joint operation with NAOMI. [ JPEG | TIFF ]

OASIS offers a range of spatial and spectral resolutions. An area of sky between 3 and 16 arcsec in diameter (4 enlarger options) can be imaged onto the array of 1100 lenslets in the focal plane. Six grisms provide spectral resolutions in the range 1000<R<4000. The 1100 resulting spectra are imaged onto a deep-depletion MIT/LL CCD, with dispersion 1 to 4 Å/pixel (15m pixels). The CCD has high QE (0.9 at 0.75 microns) and low readout noise (2.3 electrons rms in slow mode). The fringing level is low, ~3% at 0.8m, and ~10% peak-to-peak at 1m. A version of CFHT’s XOASIS data reduction package is available at ING for reduction of OASIS data. OASIS can also be used in imaging mode (primarily for target acquisition), with a field diameter of 38 arcsec. Further information about OASIS can be found on the web page: http://www.ing.iac.es/Astronomy/instruments/oasis/index.html.

OASIS can be used with or without AO correction. NAOMI typically delivers a reduction in FWHM of a few tenths of an arcsec at wavelengths 0.6–1.0m. The best corrected seeing achieved during the July 2003 OASIS commissioning was 0.3arcsec. Guide stars must currently be brighter than V~13. The guide object may also be a galaxy nucleus, if sufficiently compact. Some correction is achieved even when the science target lies several 10s of arcsec from the guide star. Performance and throughput are expected to be at least as good as achieved at CFHT. Information about NAOMI can be found on the web page: http://www.ing.iac.es/Astronomy/instruments/naomi/index.html. ¤

Email contact: Chris Benn (crb@ing.iac.es)

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Last modified: 13 December 2010