Spectrometer Specifications

The Instrument uses a fixed width slit, three prisms to cross disperse the light into at least 5 orders across the science detector, and a mid resolution grating. In addition, the first fold mirror is mounted on a piezo tip-tilt stage (S-340) to minimize the effects of flexure (FCS).


Spectrograph schematics from Wilson et al. 2004


3D representation showing the tip-tilt mirror.

Slit

The instrument has a fixed slit of 0.55" width and 18" in length. It is made of a reflective material.

In early 2018 we detected an imperfection in the slit. The effect of this imperfection is to show a trace on the dome flats. The follwing drawing (all dimensions are in units of arcseconds) shows the position of the imperfection (shown as a triangle). If possible, we suggest to avoid the compromised section of the slit.

Prisms

Two first two prisms are made of ZnSe with a 22 degree apex. The third prism is made of Infrasil with 50 degrees apex.

Grating

Grating
Name
Grooves
[l mm-1]
Sampling
[pix per resolution element]
Blaze Wavelength
[micron]
Blaze Angle
[degree]
Spectral Resolution
Peak Efficiency within each order Notes
110 110 2.7 6.98130 22 2700
See plot below
55% at 825nm, 52% at 930nm, 55% at 1100nm, 60% at 1350nm, and 79% at 1725nm. made by Newport


Spectral resolution as a function of wavelength and order for a 0.55 arcsec slit.

Final Spectrum

The dispersed light is focused by a 7-element camera onto the detector. The following is a 700 seconds exposure obtained at CIT. The spectrum shows five cross-dispersed orders that almost (small gap from 1.85 to 1.88 microns) continously cover the near-IR spectrum from the Y band (order 7 at the bottom) to the K band (order 3 at the top).


NIRES spectra

Plot of the cross dispersed orders (Wilson et al. 2004).

Go To:
Instruments Home Page       Keck Home Page       Observer's Reference Shelf


Last modified: 09/20/2018 08:05
Send questions or comments to:NIRES Support

The information on this page is the property of the W. M. Keck Observatory. The contents of this page or any part thereof shall not be copied or otherwise reproduced or transferred to other documents or used or disclosed to others for any purpose other than observing support at the W. M. Keck Observatory and the subsequent analysis and publication of scientific data obtained from observations conducted at the W. M. Keck Observatory. All rights reserved. © W. M. Keck Observatory.