Utilizamos cookies propias y de terceros para el correcto funcionamiento del sitio web y mejorar nuestros servicios. Pulse el siguiente botón para aceptar su uso. Puede cambiar la configuración u obtener más información en nuestra Política de cookies.
We use our own and third-party cookies for the correct functioning of the website and to improve our services. Click the following button to accept its use. You can change the settings or obtain more information in our Cookies Policy.
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 (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. ¤