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| Upper
End |
The new prime focus upper end
(PFUE) has been designed at CFHT with the help
of INSU-Division Technique: a new
base ring, a new set of spiders, and a prime focus base which will receive
all the other components of MegaPrime. The PFUE has been built on the West
Coast of the USA by L&F Ind.
In addition to its basic structure, the PFUE provides a temperature controlled environment for MegaCam and its readout electronics. A temperature controlled enclosure for the electronics of MegaPrime is installed on the telescope "caisson central" .
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| Wide
Field Corrector |
The parabolic main mirror of the telescope does not
produce, alone, a good image of the whole field of view; a Wide
Field Corrector (WFC) is installed in front of the camera. The WFC
has been designed at HIA (Victoria, Canada).
The lenses have been fabricated by SAGEM/REOSC, which also built
the mechanical structure of the WFC and coated the lenses.
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| Image
Stabilizing Unit |
The Image Stabilizing Unit (ISU) has been designed
and built at Observatoire de Paris. It is used
to produce small image position correction on the focal plane of MegaCam:
a
glass plate in the optical beam in front the camera can be tilted and its
produces a displacement of the image proportional to the small angle of
the tilt.
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| Focus
Stage/ Guiding Focus Sensing |
The Focus Stage Assembly
(FSA) is supporting the camera and allows its motion along the optical
axis in order to accommodate the focus variation due mainly to filter changes
and temperature induced telescope dilatation. Two guiders (GFSU) located
under the top plate of the FSA give a position and focus information from
two guide stars on the North and South edges of the MegaCam field of view.
The FSA and GFSU hardware have been designed and built at HIA, while the the control has been designed and realized at CFHT.
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| CCDs | Charge Coupled Devices
(CCDs) are the detector of choice in astronomy for observations in visible
light. Appeared in the early eighties, they have since replaced the photographic
plates or films used in astronomy for more than a century. The CCDs used
for MegaPrime have been built by e2v technologies.
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| MegaCam | At the heart of MegaPrime is MegaCam,
a unique camera built by the "Département
d'Astrophysique, de Physique des Particules, de Physique Nucléaire
et de l'Instrumentation Associée" at the French "Commissariat
à l'Energie Atomique" (CEA). In addition to a cryostat housing the
mosaic, and its criogenics system to maintain it cold, CEA built the camera
shutter, the filter jukebox and the electonics to acquire the image and
and send it to a computer through fiber optics cables.
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