SDSS

The 2.5 m Sloan telescope at Apache Point, joined by the du Pont 2.5 m at Las Campanas from SDSS-IV. SDSS imaged about a third of the sky in ugriz and took spectra of millions of galaxies, quasars and stars, the basis of the BOSS and eBOSS BAObaryon acoustic oscillationsA preferred separation of about 150 Mpc (comoving) in the galaxy distribution, imprinted by sound waves in the early Universe. Measuring it at many redshifts traces the expansion history like a standard ruler. measurements; APOGEE added R ≈ 22,500 H-band spectra of Milky Way giants. SDSS-V uses robotic fibre positionersmulti-object spectroscopyTaking spectra of many chosen targets in one field at once, through fibres placed by robotic positioners (DESI, SDSS-V) or through programmable slits and shutters (JWST NIRSpec). The basis of redshift surveys. in both hemispheres for its Milky Way Mapper and Black Hole Mapper.

Operator

Alfred P. Sloan Foundation, SDSS collaboration

Site

Apache Point, New Mexico and Las Campanas, Chile

Aperture

2.5 m

Optical spectrographs

360 nm – 1000 nm

APOGEE

1.51 µm – 1.70 µm

Survey start

April 2000