The Sloan Foundation 2.5m telescope was built in the 1990s to implement the Sloan Digital Sky Survey (SDSS). SDSS surveys are funded by a consortium of partners that have included the Sloan Foundation, many University partners around the world, and some government agencies. SDSS projects are funded for a fixed length of time, and SDSS is currently in its fifth (SDSS-V) stage of surveys! SDSS projects have been some of the most scientifically productive in the world, and SDSS has been a pioneer of survey science.
The 2.5m telescope is designed to provide high quality images over a very wide 3-degree field of view. In the early stages of SDSS, a large imaging camera was used to image a large fraction of the northern sky, but since the late 2000s, the telescope has been used exclusively for wide-field spectroscopic observations, with fiber fed spectrographs. Until the 2020s, this was achieved using spectroscopic plug plates, but this is now achieved using robotic fiber positioners, which allow for reconfiguration of fibers for targets in different regions of the sky in just a few minutes.
