Download spreadsheet for calculation of NIRSPEC sensitivities and throughputs here

High-resolution Spectroscopy


SEEING-LIMITED SENSITIVITY: Cross Dispersed, High-resolution, Reduced Spectra (sky subtracted & extracted)
Filter source mag. itime(sec) x coadd slit (") seeing (") λ + order measured SNR/pix Mag. for SNR=100 in 1 hr (1 sigma/pix) Zero Point Magnitiudes Total Throughput (%)
NIRSPEC-1 FS126 Y=˜12.3 59.0 x 1 0.720 x 12 0.78 1.089μm m=70 36 13.67 16.3 19.5
NIRSPEC-3 FS126 J=12.3 59.0 x 1 0.720 x 12 0.73 1.250μm m=61 49 13.76 16.45 22.3
NIRSPEC-5 FS126 H=11.8 59.0 x 1 0.720 x 12 0.59 1.656μm m=46 37 12.9 15.4 12.7
NIRSPEC-7 FS126 K=11.6 90.0 x 1 0.720 x 12 0.74 2.177μm m=35 50 12.9 15.4 20.2
Kband-new FS126 K=11.6 90.0 x 1 0.720 x 12 0.65 2.177μm m=35 61 13.1 15.8 29.1
KL HD84800 L=7.55 44.25 x 3 0.720 x 24 0.73 3.465μm m=22 163 10.5 14.8 28.7
M-wide HR84800 M=7.56 1.48 x 10 0.720 x 24 n/a 4.78μm m=16 8 7.8 13.8 18.4

AO SENSITIVITY: Cross Dispersed, High-resolution, Reduced Spectra (sky subtracted & extracted)
Filter source mag. itime(sec) x coadd slit (") spatial FWHM (") λ + order measured SNR/pix Mag. for SNR=100 in 1 hr (1 sigma/pix) Zero Point Magnitiudes Total Throughput (%)
NIRSPEC-1 FS2 Y=˜10.7 239.0 x 1 0.0679 x 1.13 0.064 1.089μm m=70 57 11.5 13.6 1.8
NIRSPEC-3 FS2 J=10.7 239.0 x 1 0.0679 x 1.13 0.067 1.250μm m=61 63 11.7 13.9 2.1
NIRSPEC-5 FS2 H=10.5 239.0 x 1 0.0679 x 1.13 0.053 1.656μm m=46 62 11.4 13.7 2.7
NIRSPEC-7 FS2 K=10.8 239.0 x 1 0.0679 x 1.13 0.060 2.177μm m=35 74 11.6 14.0 5.7
Kband-new FS2 K=10.8 239.0 x 1 0.0679 x 1.13 0.073 2.177μm m=35 78 11.6 14.1 6.2
KL HD203856 L=6.9 59.0 x 1 0.0679 x 1.13 0.064 3.465μm m=22 110 9.2 12.7 4.2
M-wide HD203856 M=6.8 19.2 x 2 0.0679 x 1.13 0.071 4.78μm m=16 28 7.9 11.9 3.5

Low-resolution Spectroscopy


SEEING-LIMITED SENSITIVITY: Single Order, Low-resolution, Reduced Spectra (sky subtracted & extracted)
Filter source mag. itime(sec) x coadd slit (") seeing (") λ measured SNR/pix Mag. for SNR=100 in 1 hr (1 sigma/pix) Zero Point Magnitiudes Total Throughput (%)
NIRSPEC-1 HIP 24508 Y=˜8.72 4.4 x 1 0.380 x 42 1.07 1.089μm 149 12.7 17.9
NIRSPEC-3 GD 71 J=13.72 119.5 x 1 0.57 x 42 0.59 1.250μm 138 15.9 19.2 18.1
NIRSPEC-5 GD 71 H=13.90 119.5 x 1 0.57 x 42 0.46 1.656μm 72 15.4 18.1 11.8
NIRSPEC-7 FS126 K=11.65 19.2 x 1 0.76 x 42 0.46 2.177μm 112 14.6 18.7 32.9
Kband-new FS126 K=11.65 19.2 x 1 0.76 x 42 0.46 2.177μm 129 14.8 19.0 42.6

AO SENSITIVITY: Single Order, Low-resolution, Reduced Spectra (sky subtracted & extracted)
Filter source mag. itime(sec) x coadd slit (") spatial FWMH (") λ measured SNR/pix Mag. for SNR=100 in 1 hr (1 sigma/pix) Zero Point Magnitiudes Total Throughput
NIRSPEC-1 FS2 Y=˜10.7 90.0 x 1 0.0717 x 3.96 0.087 1.089μm 169 13.3 16.9 2.7
NIRSPEC-3 FS2 J=10.7 90.0 x 1 0.0717 x 3.96 0.086 1.250μm 211 13.5 17.4 3.7
NIRSPEC-5 FS2 H=10.5 90.0 x 1 0.0717 x 3.96 0.066 1.656μm 150 12.9 16.5 3.0
NIRSPEC-7 FS2 K=10.4 59.0 x 1 0.0717 x 3.96 0.056 2.177μm 149 13.1 16.9 6.3
Kband-new FS2 K=10.4 59.0 x 1 0.0717 x 3.96 0.061 2.177μm 152 13.1 16.9 6.5
KL FS107 L=9.9 4.4 x 10 0.0717 x 3.96 0.077 3.463μm 62 11.8 15.8 4.1
M-wide HIP18907 M=3.8 2.95 x 5 0.0717 x 3.96 0.100 4.762μm 466 8.4 14.4 2.9

Theoretical Sensitivity Formulation

The following relation can be used to estimate the SNR/pixel values in other observing cases from raw frames:


                 Sgt                   S = source count rate (ADU/s)
SNR =   ______________________   where     B = Background count rate (ADU/s)
         ______________________          D = dark current (0.1 e-/s/pix)
        /                                g = gain (2.85 e-/ADU for SPEC)
             / Sgt + Bgt + Dt + r^2            t = integration time (itime x coadds)
                             \/                                  r = read noise ( 2 x (10.8 e-)^2 = 467 e- for nod pair)