
CAFOS (Calar Alto Faint Object Spectrograph), is a focal-reducer which changes the 2.2m telescope's f-ratio from f/8 to f/4.4. With imaging, spectroscopy, polarimetry and Fabry-Pérot-Etalon capabilities, designed to work in visible light.
Available at: Cassegrain station of the Zeiss 2.2 m reflector
Contact: 
In a nutshell
Direct Imaging:
 Scale: 45.3 µm/" or 0.53"/pix
FoV: 16' diameter 
 Filters: Standard filters (Johnson, Cousins, Gunn, SDSS) and  a large set
 of interference filters are available.
Spectroscopy:
 Slit: 11' length and variable width, 0.6" to 12". CAUTION: the center of the slit changes with its width! 
 Grisms: Three grism sets (400Å/mm, 200Å /mm, 100Å /mm) provide spectral dispersions of ~10Å /pix, ~4.5Å /pix and ~2Å /pix, at different wavelength ranges.
Polarimetry:
 CAFOS is equipped with a Wollaston prism and a rotatable λ/2 plate that provides:
 Imaging polarimetry: With or without a stripe mask, two polarized images separated 18".
 Spectropolarimetry: In combination with the grisms mentioned above.
Fabry-Pérot Etalon:
 Narrow band images in the 600 < λ < 1000 nm region at a resolution of R = λ/Dλ = 500.
Observing with CAFOS
CAFOS user guide 
pdf version
 Overview
 Exposure Time calculator for Imaging and Spectroscopy 
 Dome Flat Fields with CAFOS 
 Requesting observation time with CAFOS
 Service mode observing template for Imaging and Spectroscopy
 Night logsheet
More information
Technical data
Detector characteristics
 Zero points
 Atlas of lines of the calibration lamps
 Characterisarion of the CAFOS linear spectropolarimeter
Calar Alto Press releases
Possible satellite detected around the Trans-Neotunian object Varuna
 Polarized light from a brown dwarf: where lies the dust at play ?
 Calar Alto Observatory has embarked on an ambitious project with the University of Peking for the study of black holes
 Rewinding stellar evolution: The last 400,000 years of mass loss from a star
 A "hot Jupiter"challenges planetary formation theories
 The fastest stars in the universe
 Asymmetric supernova explosions
 A new class of dim supernovae
Echoes from the past
18 billion of suns support Esintein
 The faintest globular clusters of the Galaxy
 Deep Impact space mission from Calar Alto
 Formidable explosions
 The most luminous quasar state ever observed
The instrument has been founded by the Spanish Ministery of Science ICTS project ICTS-2009-32 (using FEDER funds). Fondo Europ eo de Desarrollo Regional, "Una manera de hacer Europa".
 

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