Cats Eye, excellent performance thanks to superb mechanics

The Cats Eye is an optical instrument for ESO, and is part of the Very Large Telescope Interferometer (VLTI). This system is built on top of the mountain Cerro Paranal in the Attacama desert in Chile. The delay lines, and in particular the Cats Eyes, make sure that the optical path length through telescope 1 and 2 from the incoming wavefront to the detector is identical to within 20 nm.