A powerful new fibre-fed multi-object spectrograph, WEAVE, has been mounted at the prime focus of the WHT. The large-integral-field (LIFU) mode has been commissioned, and dedicated science surveys in this mode have already begun. Pre-commissioning tests of the multi-object functionality are ongoing, and will be followed by on-sky commissioning of these modes.

After the commissioning of WEAVE, 70% of the time on the telescope will be used to carry out the dedicated surveys with WEAVE. The remaining 30% of the time is open time, available to the community. During 2024 and 2025, open-time observations will be carried out with WEAVE only. Thereafter, there is a possibility that WEAVE will be removed at intervals to allow open-time observations with non-WEAVE instruments (e.g. ISIS, ACAM and visiting instruments) but this depends on a number of factors, including the overheads (in lost observing time) associated with unmounting and re-mounting WEAVE.

The application procedure for WEAVE open time is documented here.

The median seeing at the WHT is 0.8 arcsec during April - November. The dark-of-moon sky brightness at high ecliptic latitude is similar to that at other good dark sites, V ~ 21.9 mag arcsec².

News:

2024 September 16: Start of stand-down to investigate spectrograph alignment. Expected duration: several weeks. Tests of the fibre-positioning system continue.

2023 October WEAVE (LIFU-mode) survey and open-time observations begin. Pre-commissioning tests of MOS mode continue.

2023 August: Commissioning of the LIFU (large integral-field unit) mode of WEAVE was completed early in 2023. This mode is offered in open time in 2023B and 2024A. Pre-commissioning and commissioning tests of the MOS and mIFU modes of WEAVE continue.

2022 September 29: On-sky commissioning of the LIFU mode of WEAVE begins, in parallel with pre-commissioning tests of the fibre-positioning system (for the MOS and mIFU modes).

2022 summer: WEAVE sub-systems assembled on the WHT, pre-commissioning tests begin.

2020 February 17: Start of pre-WEAVE standdown for preparation of telescope, and integration and testing of WEAVE components. This will be followed by on-sky commissioning and science verification.

2020 February 17: Last night of pre-WEAVE observing before standdown.

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