Last update: Fri Jul 19 10:19:38 HST 2024

The state-of-the-art in wide-field imaging at CFHT

MegaPrime/MegaCam is the wide-field optical imaging facility at CFHT. It represented a major upgrade of the telescope upper-end as well as the largest astronomical CCD mosaic ever built at the time of the official first light in January 2003 and for many years that followed.

The wide-field imager, MegaCam (built by CEA, Saclay, France), consists of 40 2048 x 4612 pixel CCDs (a total of 378 megapixels), covering a full 1 x 1 square degree field-of-view with a resolution of 0.187 arcsecond per pixel to properly sample the 0.7 arcsecond median seeing offered by the CFHT at Mauna Kea. The new prime focus upper end, MegaPrime, includes an image stabilization unit and a guide/autofocus unit with two independent guide CCD detectors.

MegaCam is an optical & near infrared instrument mounted on the telescope for 10 to 18 days periods centered on the new Moon. It uses most of the telescope dark time to conduct Principal Investigators led scientific programs as well as large programs or surveys such as the CFHT Legacy Survey which represented a total of 450 nights over five years between 2003 and 2009.

MegaPrime/MegaCam is operated exclusively through the CFHT New Observing Process (NOP). Observations are carried out through Queued Service Observing (QSO), the data are pre-processed (removal of the instrumental signature) and calibrated (photometry and astrometry) by Elixir, and eventually made available online to the Principal Investigators through the Data Archiving & Distribution System (DADS). The raw and Elixir pre-processed data are archived at the Canadian Astronomy Data Centre (CADC) in Victoria, and become public after a one year proprietary period. The Terapix data processing center based in Paris, primarily focused on handling the CFHTLS data, also proposes its services to the whole CFHT community with the MegaCam data stacking, fine astrometric calibration and catalogs generation.

MegaPrime is a CFHT project, funded through the instrumentation fund by the Canadian and French Agencies (NRC and CNRS/INSU). The Observatoire de Paris and HIA (Victoria) have been contracted for the design and fabrication of some of the MegaPrime components. MegaCam was built in France by CEA (Saclay). The section "Instrument Description" covers in detail the various parts of the instrument and the entities responsible for building them.

Note to the Principal Investigators preparing a time proposal: all the information relevant to the preparation of a time proposal and/or preparing the time distribution for the QSO's PH2 phase can be found in the "Specifications & Performance" and "Observing Process" sections in the left menu (instrument specifications, exposure time calculator, etc...).