MegaPrime/MegaCam Home CFHT Home General Information Instrument Description Press Release April 8, 2003 Publications Acknowledgment Text Specifications & Performance Quick Performance Summary General Summary Technical Considerations Off-field bright stars immunity Shutter ballistics Baffling & pinhole mask On-sky Instrument History Observing Runs Observing Statistics Observing Statistics II Upgrades & Problems Zeropoint History New Observing Process Exposure Time Calculator Mapping Stars & Pointings Queued Service Observing QSO PH2 SkyProbe Data Preprocessing & Calibration Elixir System Information Raw Data Description CFHT Data Preprocessing CFHT Data Calibration CFHT MetaData Products Raw & Elixir FITS headers Elixir Releases History Elixir Real-Time Elixir RT Field Guide Elixir RT Status Flat-Fields Status Standards Status Instrument Operations Cooling Status Cryostat Status External Related Sites Data Archiving at CADC Data Processing at Terapix Contacts Support Astronomer

MegaPrime/MegaCam - General Specifications & Performance Starting with semester 2015A, Megacam "ears", consisting of four additional CCDs on the side of the focal plane, are being used, to take advantage of the larger, new set of broad and narrow band filters acquired late 2014. The old broad band filters are now renamed with a trailing S: uS,gS,rS,iS,zS, while the new broad band filters are simply named u,g,r,i,z. The reference photometric magnitudes are the AB magnitude in the old (S) filters (SNLS magnitudes). The old CFH12K narrow band filters are not offered anymore. Sky background values and airmass terms for the new filters will be updated as statistics become available. Geometry Number of detectors 40 (ears included with new filters, vignetted by old (S) filters) Detector size (pixel) 2048 x 4612 Pixel size (um) 13.5 Pixel scale @ center of the field (arcsec / pixel) 0.187 Camera field of view 0.96 deg x 0.94 deg (without ears) Camera rotation No rotation - Alignment from run to run: ~1 degree Camera orientation Aligned with North-South/East-West axis Image quality degradation from center to edges ~0.05 arcsec Median seeing at center (reduced 2003A sample) gS: 0.77 arcsec, iS: 0.66 arcsec Mosaic cosmetic quality (% of dead pixels) 0.2 Small gaps between CCDs (arcsec) ~13 (70 pixels) Large gaps (2) between CCD rows (arcsec) ~80 (425 pixels) Photometry Magnitude system AB Filters uS, gS, rS, iS, zS, u, g, r, i, z Average CCD quantum efficiency over filter (%) 63.00, 85.00, 79.00, 55.00, 20.00, 62.00, 83.00, 77.00, 59.00, 19.00 Zero points (e- / sec) at 1 airmass (Zp) 25.74, 27.00, 26.50, 26.38, 25.34, 25.78, 27.11, 26.74, 26.22, 25.02 Zero points (ADU / sec) at 1 airmass (Zp) 25.22, 26.48, 25.98, 25.86, 24.82, 25.26, 26.59, 26.22, 25.70, 24.50 (Elixir data) Gain (e- / ADU) 1.62 (CCD00) Airmass term (k) 0.350, 0.150, 0.100, 0.040, 0.030, 0.350, 0.150, 0.100, 0.040, 0.030 Color term (SNLS mags) 0.000, 0.000, 0.000, 0.000, 0.000, -.232, -.087, +.065, +.068, +.065 Color (Instrumental to SDSS system) (SDSS mag.) xx-xx, xx-xx, xx-xx, xx-xx, xx-xx, uS-gS , gS-rS , gS-rS , rS-iS , iS-zS Dark sky brightness @ zenith - Moon 0% 22.70, 22.00, 21.30, 20.30, 19.40, 22.70, 22.00, 21.30, 20.30, 19.40 (mag / arcsec^2) Grey sky brightness @ zenith - Moon 30% 21.20, 21.30, 20.80, 20.30, 19.40, 21.20, 21.30, 20.80, 20.30, 19.40 (mag / arcsec^2) Bright sky brightness @ zenith - Moon 60% 19.70, 20.50, 20.40, 20.30, 19.40, 19.70, 20.50, 20.40, 20.30, 19.40 (mag / arcsec^2) Dark sky brightness @ zenith - Moon 0% 0.580, 3.340, 4.170, 8.350, 8.350, 0.580, 3.340, 4.170, 8.350, 8.350 (e- / pixel / sec) Grey sky brightness @ zenith - Moon 30% 2.340, 6.680, 6.260, 8.350, 8.350, 2.340, 6.680, 6.260, 8.350, 8.350 (e- / pixel / sec) Bright sky brightness @ zenith - Moon 60% 9.350, 13.36, 9.390, 8.350, 8.350, 9.350, 13.36, 9.390, 8.350, 8.350 (e- / pixel / sec) Sky brightness airmass dependency (offset) 0.340, 0.340, 2.460, 11.60, 11.90 (e- / airmass / sec) Point source, SNR=10, 60mn, Dark, 0.8" 25.30, 25.70, 25.10, 24.70, 23.70, 25.60, 26.00, 25.50, 24.60, 23.40 (mag AB) Field galaxy, SNR=10, 60mn, Dark, 0.8" 25.00, 25.20, 24.60, 24.30, 23.20, 25.10, 25.60, 25.00, 24.20, 23.00 (mag AB) Transition from AB to Vega magnitude system -.346, +.092, -.171, -.401, -.554, -.621, +.087, -.181, -.392, -.526 (mag) Instrumental magnitude equation m ~ Zp[e-/sec] - 2.5log(Gain[e-/ADU]) - k(airmass - 1) OR m ~ Zp[ADU/sec] - k(airmass - 1) (Elixir data) Raw fringe amplitude ~6% in i/iS, ~15% in z/zS New narrow band filters (same FOV) Halpha, HalphaOFF, OIII, OIIIOFF, CaH&K Camera Readout time (including overhead) ~40 seconds Read noise (e- / pixel) ~5 Electronic chain gain (e- / ADU) 1.67 (0.2 dispersion over the mosaic) CCD operating temperature (deg. C) -130 Dark current (e- / pixel / minute) 0.03 Charge transfer efficiency (parallel & serial) 0.999995 Digital encoding (bit) 16 Pixel saturation (ADU) 65536 (~110,000 e-) Linearity range within ~1% (ADU) All CCDs except 12,17,23,33,28,20,13,22 (1.5-2.2%) Residual image after saturation None Crosstalk between channels None Telescope & instrument EMI noise None (any action can take place during readout) Pixel full well = blooming threshold (e-) ~150,000 FITS file Raw file format Multi Extension FITS (main header + 40 extensions) Mosaic MEF 40 extensions file size (Megabyte) ~750 Single CCD FITS image size with overscans (pixel) 2080 x 4644 Number of amplifiers per CCD image 2 (due to data splicing) Observing Immunity to bright stars scattered light Excellent Typical exposure time (second) 300 Minimum exposure time (second) 1 Shutter accuracy (second) 0.003 Uniformity of exposure over the mosaic 99% for a 1 sec exposure Filter exchange time (second) 90 Cosmic rays rate (events / CCD / minute) 150 Observing mode Exclusively Queued Service Observing (QSO) Data pre-processing Elixir at CFHT