STELLA échelle Spectrograph (SES)
The 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.