Wide - eld CCD imaging at CFHT : the MOCAM example

We describe a new 4096 4096 pixel CCD mosaic camera (MOCAM) available at the prime focus of the Canada-France-Hawaii Telescope (CFHT). The camera is a mosaic of four 2048 2048 Loral frontside-illuminated CCDs with 15 m pixels, providing a eld of view of 140 140 at a scale of 000 :21 pixel . MOCAM is equipped with B, V, R and I lters and has demonstrated image quality of 000 :5{000 :6 FWHM over the entire eld. MOCAM will also be used with the CFHT adaptive optic bonnette and will provide a eld of view of 9000 at a scale of 000 :02 pixel . MOCAM works within the CFHT Pegasus software environment and observers familiar with this system require no additional training to use this camera e ectively. The technical details, the performance and the rst images obtained on the telescope with MOCAM are presented. In particular, we discuss some important improvements with respect to the standard single-CCD FOCAM camera, such as multi-output parallel readout and dynamic anti-blooming. We also discuss critical technical issues concerning future wideeld imaging facilities at the CFHT prime focus in light of our experience with MOCAM and our recent experience with the even larger UH 8192 8192 pixel CCD mosaic camera. Subject headings: instrumentation: CCD camera, data reduction, observational techniques Visiting astronomer, Canada-France-Hawaii Telescope, operated jointly by NRC of Canada, CNRS of France and the University of