ING Banner
Home > Astronomy > ISIS

Characteristics

Applying for time

Observing

Documentation

For ING staff

Contact
Ian Skillen
ISIS Instrument Specialist
wji@ing.iac.es
Marie Karjalainen
ISIS Polarisation Specialist
ISIS/QUCAM Specialist
mh@ing.iac.es

ISIS

ISIS at the Cassegrain focus of the WHT

The Intermediate-dispersion Spectrograph and Imaging System (ISIS) is mounted at the Cassegrain focus of the 4.2m William Herschel Telescope. It is a high-efficiency, double-arm, medium-dispersion (8-121 Å/mm) spectrograph, capable of observing in a long-slit of up to ~4' length, and up to ~22" width. Use of dichroic filters permits simultaneous observing in the blue and red arms, with a ~200Å wavelength range of reduced throughput at the dichroic cross over from reflection to transmission. Both arms are optimised for their respective wavelength ranges. Linear and circular spectropolarimetry, and imaging polarimetry, modes are also available.

The default detector on the ISIS blue arm is EEV12, a thinned, blue-sensitive array of 2048×4096 (13.5 micron) pixels. The default detector on the ISIS red arm is RED+, a red-sensitive array of 2048×4096 (15.0 micron) pixels, with almost no fringing.

For fast or faint-object spectroscopy, two 1kx1k electron multiplying CCDs (EMCCDs), QUCAM2 and QUCAM3, are available for both arms of ISIS. They provide high-speed spectroscopic capability with very little dead time, and have essentially zero read noise. EMCCDs have distinctive properties, and their use depends critically on the nature of the observations. These two detectors can also be used as classical, frame-transfer CCDs.

An image slicer is available on a shared risks basis. It limits loss of light at the entrance slit of the spectrograph, allowing the maximum spectral resolution of the spectrograph to be attained with greater throughput in modest seeing conditions.

The ageing but venerated RGO 4.2m Microprocessor System (4MS) controllers were replaced by a Programmable Logic Controller (PLC) system in 2012, and this has enabled faster movement of ISIS mechanisms with improved reliability.



Top | Back

Contact:  (ISIS Instrument Specialist)
Last modified: 28 November 2018