NOTcam spectroscopy: flux calibration

From data obtained on 2/7/2004, of the optical flux standard BD+26 2606 (G166-45; SP1446+259; V=9.7, J=8.7, H= 8.4, K=8.4 Alonso et al. 1994 A&ASS 107, 365), with the widest 'slit' (1mm pinhole), grism #1 and WFC, we obtained the following preliminary results.

At 1250 nm (approximate center of J band), the system efficiency (atmosphere, telescope, instrument, detector) is about 4%. At 1030 nm (approximate center of the Y_n filter NOT #222), the system efficiency is about 3%, but these 3% are divided over the 6th and 7th order. Extrapolating this to H and K, using estimates for instrument and detector efficiencies, we get a total system efficiency for H and K of 5% and 6% respectively.

In the J band (6th order), the above star gives about 110 electrons/Angstrom/second, in the reduced spectrum. In the Z band (Y_n filter, 1030nm, 7th order) we get about 75 e-/A/s. In the H band we observed approx 90 e-/A/s. In K we observed about 70 e-/A/s.

Science-grade array

I have extrapolated the above results to derive estimates for the spectroscopic JHK efficiencies and countrates when using the new science array (installed Dec. 2007).

Expected count rates and efficiencies for science-grade array
	J band	H band	K band
system efficiency	7%	8%	9%
photons/sec/Å   for SP1446+259	190	140	105

In June 2009 the star SP2209+178 was observed to calibrate the Y_n-band efficiency.

Measured efficiency for science-grade array
date	Yn band 7th order	Yn band 6th order	J band 6th order	J band 5th order
June 2009	3.5%	4.7%	6.3%	8.2%

In June 2011 the star SP2209+178 was observed to calibrate the Y- and Z-band efficiency.

Measured efficiency for science-grade array
date	Z band 8th order	Z band 7th order	Y band 7th order	Y band 6th order	J band 6th order	J band 5th order	H band	K band
12 June 2011	3.7%	3.5%	4.7%	4.6%	4.5%	6.3%	7.0%	5.6%

Exposure-time calculator

Currently, the above estimated efficiencies and countrates for the science-grade array are used in the exposure-time calculator.