CISCO sky spectra

Wavelength calibration

Since each grating covers the entire wavelength range admitted by its order sorting filter, the mapping between pixel and wavelength is fixed. The following are quadratic fits (wavelength = c + b x + a x2) for the wavelength (in um) as a function of pixel (x) for the three grisms in case of the slit center is 524 pixel at y=512.

zJ grism: 0.84411 + 5.11791e-4 x + 3.99912e-8 x2
JH grism: 1.01627 + 8.15683e-4 x + 3.74330e-8 x2
wK grism: 1.70271 + 8.23663e-4 x + 7.04097e-8 x2

Grism: zJ   JH   wK
Pixel: Wavelength: um
If the slit center is not 524, modify three coefficients to the following rerlation:
a' = a
b'=b-2 a dx
c' = c - a dx2 - (b - 2 a dx) dx
dx = (new slit center at y = 512) - 524

revised 2003 Dec. 5

Sky spectra

You can perform your own wavelength calibration of CISCO spectra by using the night sky lines. The following plots show typical sky spectra taken with a 1.0'' slit. Postscript plots of the zJ, JH, and wK sky spectra are also available.

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