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.
Version 2.25 of the data reduction pipeline has been released. It includes some enhancements from the previous version, outstading the new and more reliable method for fibre tracing, the automatic detection of CCD type, allowing reduction of data taken with either
WHTWFC or RED+4, and the IRAF compatible final products.
AF2/WYFFOS has received several performance-enhancing
upgrades during 2013A, and is offered to observers for 2014A.
(1) The rms accuracy with which science targets can be
acquired onto fibres has been substantially improved, via:
implementation of a new automatic field-acquisition tool;
better characterisation of geometric distortions in the focal plane;
and an improved algorithm for fibre placement.
(2) A new 4k x 4k red-sensitive CCD with very low-fringing, Red+4, has
been successfully commissioned and is offered as the default
detector for WYFFOS.
(3) New calibration lamps (a QTH continuum lamp and ThAr, Cd
and Zn arc lamps), have been purchased and tested.
In addition, an extensive investigation of the throughput of AF2/WYFFOS
has been carried out, including on-sky throughput measurements with
both the Red+4 and WHTWFC detectors, and microscopic inspection of all
fibre input-end microprisms.
A more detailed description of the recent enhancements and investigations
can be found here.
Teams considering submission of an AF2 proposal are encouraged to
contact the AF2 instrument specialist if they have any queries.