CFHT operating manual - Homepage Usask

CFHT Observatory Manual - Observatory (Sec.5) http://www.cfht.hawaii.edu/Instruments/ObservatoryManual/CFH...
mirror train with optical fibers. CAFE consists of an optical bench mounted to a port
on the Cassegrain Bonnette, two fiber optic cables and a Bowen-Wallraven slicer for
injecting the beam into the Gecko Spectrograph.
A "fiber agitator" (which agitates the optical fiber with an amplitude of 1 mm and a
frequency of 30 Hz) has been installed to prevent modal noise and the S/N
degradation associated with it. Flat field correction seems to be better than with the
coudé mirror train.
CAFE - (A Fiber Feed to Gecko)
The CAFE is an instrument that replaces the old coude mirror train with a fiber optic.
The project consists of 3 pieces:
1) An optical bench mounted to a port on the Cassegrain Bonnette which contains a
holder for the fiber, feed optics for the fiber, flat field and spectral (ThAr) calibration
lamps, feed optics for the calibration lamps, and a mechanism to select between
telescope feed and calibration feed. The light from the telescope is fed into this
optical bench using the Cassegrain Bonnette central mirror. The electronics for the
optical bench is controlled from a crate mounted on the Cassegrain environment.
2) Two fiber optic cables (one for spare) with microlenses on either end to shape the
beam. The fibers are ~28 m long.
3) Optics for injecting the beam into the Gecko Spectrograph. This is a
Bowen-Wallraven slicer to which the fiber cable is attached. The beam is injected
into the spectrograph at f/20 as is was the case with the coude train.
The CAFE was built for CFHT by Jacques Baudrand, Rene Vitry, and Michel
Lesserter at the Observatoire de Paris-Meudon.
CAFE was first delivered to CFHT at the end of September 1999 and a preliminary
acceptance test was held at CFHT with Jacques Baudrand and Rene Vitry of OPM
during the last two weeks of October. The tests went well with much progress being
made on the controller software in the two weeks Jacques and Rene were here.
Optically and mechanically, CAFE was shown to be very stable and reliable.
CAFE returned to CFHT in mid-2000 and was used for the first time for science in
July 2000. CAFE is now a commissioned instrument at CFHT and is the primary feed
for Gecko.
Filters
The CFHT filter list is available in a companion document (CFHT Filters).
Grisms
The MOS/OSIS grism information is provided in two tables, one for MOS/OSIS
visible, the other one for OSIS-IR.
Gumball
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