STELLA échelle Spectrograph (SES)
A view into SES, the optical fiber is visible in the center of the image, the grating is at the right side, the cross dispersers and camera optics to the left.
Credit: AIPThe SES is a modern white-pupil spectrograph with a moderately high spectral resolution of about 55,000 and a fixed wavelength format of 390 to 870nm. The instrument is located on a passively stabilized optical bench in an insulated box within an actively temperature-controlled room. It is fed by a 24m long octagonal optical fiber with 50µm core diameter. The spectrograph consists of a 31 lines per mm R2 echelle grating from RGL, two off-axis parabolic collimator mirrors, one folding mirror and two prisms acting as cross-disperser. The beam with a diameter of 130mm is imaged onto the detector by a f/4 refracting camera. A 4x4k E2V CCD together with a AIP-built Magellan controller is used as the detector system. The readout noise of the CCD is about 3.5 electrons rms, a CryoTiger closed cycle cooler keeps the CCD temperature at -120°C.