The MUSE (Multi Unit Spectroscopic Explorer) instrument on ESO’s Very Large Telescope (VLT) works with an adaptive optics unit called GALACSI. This makes use of the Laser Guide Star Facility, 4LGSF, a subsystem of the Adaptive Optics Facility (AOF). The AOF provides adaptive optics for instruments on the VLTs Unit Telescope 4 (UT4). MUSE was the first instrument to benefit from this new facility and it now has two adaptive optics modes — the Wide Field Mode and the Narrow Field Mode.

The MUSE Wide Field Mode coupled to GALACSI in ground-layer mode corrects for the effects of atmospheric turbulence up to one kilometre above the telescope over a comparatively wide field of view. But the new Narrow Field Mode using laser tomography corrects for almost all of the atmospheric turbulence above the telescope to create much sharper images, but over a smaller region of the sky.