Applying for Time
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ING Newsletter No. 9, March 2005

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Reference: ING Newsl., No. 9, page 37.
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Applying for Time

Danny Lennon (Head of Astronomy, ING)*

Over the years the instrument suite at the WHT has changed many times. One constant in all these changes is that our intermediate dispersion spectrograph ISIS continues to win the largest share of the observing time across all our three TACs. It’s therefore good to see some improvements coming to this venerable instrument. The past 6 months have seen the commissioning of a new dichroic beam splitter, and initial tests indicate that the infamous ripples which plagued the old dichroic set are substantially reduced. Throughput in both blue and red arms is improved, while the response of the new blue fold mirror is also substantially better than before (details may be found on the ISIS web pages). This is the only dichroic which will be offered in service mode, and will be the default dichroic offered to visiting observers unless an alternative is specified. It is expected that the older dichroics will be phased out of use pending feedback from users.

We have also commissioned the new ISIS TV slit viewing camera, discussed in the article by Simon Tulloch in ING Newsletter, 8, 20. This camera is based on a Peltier cooled frame transfer CCD, and can be controlled in much the same way as any other CCD at the ING. Besides offering better image quality and improved ease of acquisition for ISIS it offers the additional advantage that one can now take an acquisition image of the slit during a science exposure. Finally during the coming year we expect to see the image slicer commissioned on ISIS, this will have a 2 arcsec entrance aperture and a 0.5 arcsec sliced output image, nicely matched to the optimum resolution of the ISIS CCDs.

The digital media storage landscape continues to change very rapidly, which is just as well given the increasing rate of data acquisition in astronomy. A number of survey programmes using the WFC on the INT have highlighted this issue recently due to their extremely high data rates (and short exposure times), and the ING now has a provision to allow users to copy their data to external firewire discs. If users can demonstrate a clear need for this facility on the INT and wish to avail themselves of the service they should contact Robert Greimel (

Despite some minor teething problems during 2004B, LIRIS continues to perform very well at Cassegrain. We will therefore continue with our policy of only offering LIRIS for use at this focal station for IR imaging (and spectroscopy), INGRID will continue to be used with NAOMI, our natural guide star AO system. OASIS is performing as expected, however it should be noted that with OASIS there is the choice of using the instrument with or without AO correction. Furthermore, during 2005A, we expect to finish commissioning a mode of operation in which only tip-tilt correction is applied, somewhat relaxing the constraint on the magnitude of the guide star while still providing attractive performance in the I-band.

The Director’s Message has already referred to the questionnaire which has been released by ING in order to gauge the views of the astronomical community on the future of the observatory. While individual responses are confidential, the overall results will be fed into the ING review process later this year and will have an influence on the future development of ING and its instrumentation suite. For example, the default situation on the future for the WHT is essentially the continuation of the existing suite of instruments, which now comprises optical and IR imaging and spectroscopic capability, multi-object spectroscopy, and adaptive optics (AO) at optical and IR wavelengths. Our ongoing development currently focuses on extending the use of the AO suite through the use of a Rayleigh laser beacon which will dramatically increase the sky coverage and hence the scientific potential of the existing AO system. The INT is currently a single instrument telescope, utilising the Wide Field Camera, and no change in this status is as yet decided upon. It is very important therefore that our users complete and submit the questionnaire if they wish to have their say on the future of ING. ¤

*: Email contact: Danny Lennon (

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