WHT report for period 1996 Jan 1 - Aug 31 Telescope downtime due to technical problems averaged 3% during this period (it has been below 5% for 4 years). Various one-off and intermittent software and hardware faults are responsible for this residual downtime; no particular subsystem dominates the statistics. The telescope mirrors have been cleaned regularly with CO2 snow since last autumn; this has proved very effective at removing dust. The Nasmyth flat mirror was re-aluminised in March, for the first time in 6 years (the primary and secondary were re-aluminised last autumn). A new ISIS polarisation module, with better mechanical reliability and more accurate rotaton of the plates, was successfully commissioned in July. WYFFOS commissioning is now complete. The recurring contamination last year of the camera's field lens was traced to the material bonding the CCD to the cold finger, and was remedied at RGO. WYFFOS was used successfully for observing in March and May 1996. The fibre gripper in the AUTOFIB fibre positioner gave some problems during the latter run, and failed completely on the last night of observing. It is being rebuilt on-island before the next observing run. In July, WHIRCAM was mounted for the first time at the Cassegrain focus, fed by one of the 45-degree mirrors in the A&G box. No astronomical commissioning has yet been carried out, but it has been confirmed that the IR background (nbL) is not significantly different from that at GHRIL. A number of engineering problems need to be solved before WHIRCAM can be offered for scheduled observing at Cassegrain. Chief of these is finding a safe way to route the helium-coolant hose to WHIRCAM while it is mounted on the rotator. The MARTINI-3 adaptive-optics system was successfully commissioned in cophased mode during 3 nights in August. Images with 0.2-arcsec FWHM were achieved over the full 13-arcsec field of view of WHIRCAM (at scale 0.05 arcsec/pixel). The WHT's first Loral CCD (2048*2048 15-micron pixels) arrived in July. It's main advantage over the TEK CCDs is a much improved UV/blue response (a factor of about 3 in the UV). Further Loral CCDs are expected on-island shortly. IPCS was used as a detector for probably the last time ever in February. A team from NAO Japan used their mosaic CCD camera (5000 x 8000 pixels) at WHT prime focus in April 1996. The (unfilled) mosaic CCD covers 30' x 50' in four exposures, i.e. most of the prime-focus field, and is a superb complement to the AUTOFIB/WYFFOS fibre-fed spectrograph. Only 1 of the 12 nights was photometric, but otherwise the run was very successful, and the camera (a prototype for the Subaru 8-m) is likely to visit the WHT again. Half-hour overrides of scheduled observing by the JOSE instrument (to evaluate the spatial and temporal scales of atmospheric turbulence above ING) began in December 1995. The overrides apply to one night of each scheduled PATT/NL run lasting more than one night, and to S/D nights. The royal opening of the Italian Galileo telescope took place on June 29. The royal party visited the Galileo mirror in the aluminising area of the WHT. Use of S/D nights during this period ------------------------------------ nights % Service 15.7 42 Telescope (pointing tests, investigating optical aberrations, focus tests) 1.6 4 Instrument quality control (throughput, alignment, commissioning new features, flux standards etc.) 10.4 28 JOSE 2.0 5 Bad weather 6.3 17 Technical problems 1.0 3 ---- --- Total 37.0 100 These numbers exclude 6 nights allocated for AUTOFIB/WYFFOS commissioning, of which 3 were lost to bad weather, and 3 nights allocated for MARTINI-3 commissioning. Chris Benn 1996 Sep 17