AutoFib2+WYFFOS (AF2) is the multi-object, wide-field,
fibre spectrograph working at the Prime focus of the 4.2m William Herschel Telescope (WHT)
. It contains
150 science fibres each of 1.6 arcsec diameter, and 10 fiducial bundles for
acquisition and guiding. At the Prime focus, the fibres are placed onto a
field plate by the robot positioner Autofib2 at user-defined sky coordinates.
Object light is transmitted along fibres 26 metres in length to the Wide
Field Fibre Optical Spectrograph (WYFFOS). The path from Prime focus to the spectrograph
consists of a prism, fibre button, 26 metres of fibre, finger, microlens
and the facet block.
The AF2/WYFFOS multi-fibre spectrograph will be available in 2013B on a shared-risks basis.
Recent work has confirmed that
imperfect acquisition and guiding were contributing significantly to the
low throughput noted by observers. Preliminary tests indicate that new procedures improve the acquisition accuracy to better than 0.4
arcsec rms out to 15 arcmin from the center (the nominal unvignetted maximum field radius is 20 arcmin), and we expect that ongoing planned work will yield further improvements before 2013B.
For reference, an offset of 0.5" leads to ~20% aperture loss from a point source (seeing of 0.5"-1.5" FWHM), when compared to the corresponding flux for a perfectly centered fibre.
We also expect to offer 2013B observers a new low-fringing detector for use with AF2: the 4k*4k REDPLUS CCD.
AF2's availability in 2013B will be on a shared-risks basis because the on-sky tests of the new acquisition software, and the commissioning of the new CCD are not yet complete.
Teams considering submission of an AF2 proposal are encouraged to notify the AF2 instrument specialist.
AF2/WYFFOS is not offered in the semester 2013A, to allow implementation of a number
of upgrades aimed at a
significant improvement in acquisition accuracy and system throughput. The
upgrades are expected to
address the low-throughput issues recently reported by observers.
November 2011: The new IDL-based reduction pipeline for AF2/WYFFOS is now available. It can be downloaded
November 02, 2010: New Solaris and Linux versions of af2_configure are available. They are able to automatically retrieve the latest AF2 fibre and telescope .dat files, and also warn you if less than 3 fiducial fibres are allocated. Also, check out the new af2_configure Users Guide.
October 20, 2010: A completely new AF2 data reduction pipeline and quicklook is under development! Based on IDL and usable through a simple GUI, it will be able to perform automatic
quicklook of your data while at the telescope, as well as full data reduction. The estimated arrival time for the pipeline is October 1, 2011.
October 20, 2010: A new Hg lamp for performing wavelength calibration in echelle mode orders 6 and 7 is available! This removes the previous limitation to use the high resolution echelle mode
with wavelengths shorter than 4500 Angstrom.