IRCS grism system efficiency

Grism observations shortward of 2.5Ám are made by selecting different orders of the light reflected from a single grism.

Observations in the thermal-infrared are made with a different grism.

The efficiencies of the new JH and HK low-resolution grisms are as follows:


zJH Grism datasheet

The appropriate order is selected by means of order sorting filters. The transmission curves for these filters was measured at ~90K, and there is a slight shift when they are cooled to 65K.

  • Order sorting filters (GIF): Iz, zJ, J, H, K
  • Order sorting filters (JPG): Iz, zJ, J, H, K


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