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Limited tests of Phoenix with the new Gemini-supplied Aladdin II array in February 2001 on Kitt Peak provided the data used for the exposure time calculator available on the NOAO web pages as of 9 August 2002. The plots below uses those estimates together with empirical data points corresponding to observations made during the May 2002A queue-observing run when available. Please note that limiting magnitudes longward of 2.5 microns are highly sensitive to the emissivity of both the telescope and (variable) atmosphere.

The delivered performance is as expected in J, H, and K, but falls short of the predicted value at M band by ~1.5mag.

These sensitivities are for the median image quality and average airmass of about 1.2. The magnitudes listed below correspond to a black body spectrum of temperature 9900 K, using the 4 pixel slit. The individual observations in J, H and K are of half the total time listed, to a maximum of 900sec or the exposure time the NOAO ITC indicated that saturation may occur, whichever was less, and all include the source by offsetting along the slit.  In the M band, all the individual observations are of 30 seconds duration. Sky subtraction noise has been considered in the calculation.

The empirical data points (filled red symbols) correspond to spectra obtained during the May 2002 science queue run. The observed central wavelength is not identical to the reference wavelength listed on the plots, but is close in all cases. The data points refer to a single target, with the image quality measured from the final spectrum profile and corrected to 1.2 airmass. Links below the figures will download postscript versions of the plots.

Sensitivity plot 1.215mu

Sensitivity at 1.215µm for J= 7 to 13mag; also available as a postscript file

Sensitivity plot 1.654mu  

Sensitivity at 1.654µm for H= 7 to 13mag; also available as a postscript file

Sensitivity plot 2.179mu  

Sensitivity at 2.179µm for K = 7 to 13mag; also available as a postscript file

Sensitivity plot 4.789mu  

Sensitivity at 4.789µm for M = 5 to 8 mag; also available as a postscript file


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Last update August 18, 2002; Cláudia Winge