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William Herschel Telescope

AUTOFIB-2: Automated Fibre Positioner

— Fiber-optics multiobject spectrograph —

First light: 12 October 1994.

De-commissioned: 31 July 2017

Designed and built by: Durham University and RGO. After commissioning the robot and fibre module were re-engineered by ING.

Description: AUTOFIB is an automatic fibre positioner that can place up to 150 fibres within the one degree field of the WHT prime focal plane. Reconfiguration under software control is designed to take 15-20 minutes.

In 1998 AUTOFIB underwent major modifications to the chassis and fibre-griper. The new system shows much improved positional accuracy of the fibres.

The small fibre (1.6 arcsec diameter) module was successfully commissioned on July 2001. The Small Fibre module contain 150 fibres with 1.6 arcsec diameter (90 micron), which run without connectors from AF2 to WYFFOS. The fibres are high-content OH fused silica made by Polymicro. Compared to the Large Fibre module, small fibres have the following main two advantages: 1) no light loss is due to fibre connectors, providing a more homogeneous distribution of fibre relative throughput; 2) the sky/background contribution in observations with the small fibres is 0.35 times smaller than with the large fibres. This means that, with the small fibres, the noise level in sky-limited observations is down by a factor of 0.6.

The Small Fibres are imaged onto less than 2 pixels (FWHM) on the TEK6 detector in the spatial and spectral directions. The full spatial image of the fibres is therefore sampled by less than 3 pixels. There may be a slight gain in S/N of the extracted spectrum with respect to the Large Fibre case, as less pixels have to be extracted when sampling the wings of the spatial profile. For Small Fibres, the fibre distance in the WYFFOS entrance slit is 1mm, which transforms onto a peak-to-peak aperture distance of 6-7 pixels on the detector.

Some scientific highlights:

Publications (scientific papers, technical publications, etc.).

Instrument information:


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Last modified: 22 August 2016