ING Annual Report 1997
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Chapter 3
Telescope Operation
TELESCOPES
The quality control programme continued
to be enhanced, in order to ensure that not just the quantity, but also
the quality of data obtained by visiting observers is maximised. The programme
includes regular checks of the telescope image quality, of the primary
mirror reflectivity, of key optical performance indicators of the main
spectrographs, and of detector performance.
Trials of queue scheduled observations were carried out with the INT prime
focus CCD mosaic imaging camera. The observations were carried out by staff
astronomers using the priority order established by the time allocation
committee. The aim was to gain experience with queue observing, in particular
in the area of pre-observing information, on-line assessment of data quality,
dissemination of data, and to assess the cost. No major problems were encountered,
and user feedback was generally positive. Results from a questionnaire
that was sent out to the user community suggests that many observers see
a worthwhile benefit in service and queue observing, in particular where
these observing modes use the valuable observing time more effectively,
and allow greater flexibility in the observing schedule. It is the intention
to explore these observing modes further.
The Richardson Brealey Spectrograph had its last observing run on the JKT
in November 1997. From then on the JKT has effectively become a single-instrument
imaging telescope, which reduced overall operational cost of this telescope.
Good progress was made on the programme to modernise and improve the control
systems of the telescopes and instruments. The ultimately aim is to have
common control systems on all three telescope based on modern equipment
and using industry standards where possible. These measures will improve
reliability and reduce the total operational cost of the telescopes.
The Telescope Control System (TCS) as well as the Instrument Control System
(ICS) on the INT were renewed. Also the Data Acquisition System (DAS) on
both the INT and the JKT were replaced by a Unix based system which resulted
in an important reduction in time loss due to acquisition overheads.
The year 1997 also saw an upgrade of the ING data archive which is based
in Cambridge. This new archive is based on the system developed by the
Canadian Astronomy Data Centre, using the Sybase commercial database, and
has also been adopted by a number of other observatories (e.g. HST, ESO,
UKIRT). There is an easy to use user interface, accessible via the World
Wide Web (http://archive.ast.cam.ac.uk/ingarch/),
and the archive provides links to other major archives. The preferred method
of disseminating requested archive data is now via ftp transfer, although
the data can be sent on DAT tape if requested. Usage of the archive doubled
shortly after introduction of the new system, and continued to rise.
During the period Feb - March 1997 the European Comet Hale-Bopp team used
the ING telescopes during their extensive observing campaign. In order
to further the scientific use of the data obtained, a Hale-Bopp archive
was set-up, containing all of the data obtained at the ING telescopes,
plus that from the other telescopes on La Palma and Tenerife. This archive
is hosted in Cambridge as part of ING's science archive.
The continuing investigation of the quality of the seeing at the observatory
has now resulted in a large dataset from the Differential Image Motion
Monitor (DIMM), as well as from Shack-Hartmann wavefront sensor experiments
at the Nasmyth focus of the WHT (JOSE). The results can be summarised as
follows. The median value of the intrinsic site seeing is 0.70 arcseconds.
There is no significant variation between different areas of the site,
as the seeing values deduced by simultaneous measurements taken at various
telescope sites are essentially the same to within approximately 0.05 arcsec.
There is a substantial seasonal variation, with a peak-to-peak amplitude
of about 0.35 arcsec.
The median value of the image quality measured through the telescope using
a Shack-Hartmann wavefront sensor (hence including contributions from dome
as well as site seeing) is about 0.75 arcsec. The small difference between
free atmosphere seeing and the seeing measured through the telescope indicates
that the William Herschel Telescope does not substantially degrade the
natural seeing. Further improvements are expected from better focussing
procedures, and improved focus-tracking models.
 |
| Histogram for JOSE (dotted line)
and DIMM (solid) contemporaneous data from all nights in 1996-98. The JOSE
experiment measures seeing from the telescope, and DIMM from outside the
dome. So this plot clearly shows that WHT dome seeing is negligible (extracted
from R W Wilson et al, MNRAS, in press). [ GIF
| TIFF ] |
An international agreement between PPARC,
NWO and the University of Porto was signed in October 1997. Under this
agreement the University of Porto obtains 28 nights of observing time on
the JKT and access to the INT and WHT under open competition with other
astronomers through the normal peer review process. In return, the University
of Porto will station one person at ING in support of the operation. This
agreement takes effect from February 1998.
OBSERVATORY INFRASTRUCTURE
The facilities for staff working in
the new sea-level offices as well as on the mountain top were further improved.
A detector clean room has been constructed which allows repairs and testing
of CCD systems under clean and controlled conditions. A detector workshop
providing an area for tests and maintenance work on detectors is under
construction in the WHT building.
The instrument test focal station on the ground floor of the WHT building
has been extended and now allows maintenance work to be carried out on
two or three instruments at the same time, and it allows for easy connection
to the observatories computing infrastructure. Full system tests can now
be carried out as if the instrument were on the telescope.
The mechanical workshop in the INT building has undergone a major reorganisation
to provide a better and more safe work environment.
New cars were acquired for visiting and support astronomers' use on site.
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Chapter
2 - New Instrumentation and Enhancements | Up: Table
of Contents | Next: Chapter 4 - Telescope Performance
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