CFHT, Instruments, Detectors, IR, CFHT-IR, Performances.

CFHT-IR

Performances

Preliminary estimation of CFHT-IR sensitivity in imaging mode

The following figures illustrate the limiting magnitudes reached by CFHT-IR for a selection of broad-band and narrow-band filters in imaging mode as a function of the observing conditions. For each figure, the resulting image is obtained by combining several individual frames and subtracting the corresponding sky frames. The elementary integration time (per frame) depends on the filter and was selected in order to fill about half of the detector capacity. Typical such elementary integration times are between 30 seconds and 2 minutes for broad-band imaging and 10 to 20 minutes for narrow-band imaging. Much shorter elementary integrations would still be limited by background shot noise rather than detector noise, but their readout overheads would become significant for the broad band filters.
 

Figure 1: CFHT-IR limiting magnitudes per square arcsecond as a function of the total integration time for extended sources (SN = 5). Click here for a printable version of the Figure.


 

Figure 2: CFHT-IR limiting magnitudes reached for point-like sources in 1 hour total integration time at SN = 5. A seeing value of 0.7" at 0.5 microns (median value for Mauna Kea) has been considered. The photometry is derived on an aperture corresponding to 1.2 x the seeing FWHM at the given wavelength. For true point sources, PSF-fitting photometry gives significantly better limiting sensitivity (by about 0.3 magnitude) than the procedure described here. Click here for a printable version of the Figure.


 

Figure 3: Evolution of the CFHT-IR limiting magnitudes as a function of the seeing value at 0.5 microns. The photometry is derived on an aperture corresponding to 1.2 x the seeing FWHM. Total integration time is 1 hour at S/N = 5 in the K' band. Click here for a printable version of the Figure.


 

Figure 4: Evolution of the CFHT-IR limiting magnitudes as a function of the diameter of the aperture used for photometry. Total integration time is 1 hour at S/N = 5 in the K' band, but the scalings between different apertures obviously are valid for any integration time and filter. Click here for a printable version of the Figure.

Created 24 August 2000.
Updated 14 February 2003.
Page created by Jean-Luc Beuzit and maintained by Thierry Forveille.
Please send comments to: forveill@cfht.hawaii.edu