Echelle Grating

The inclination angle of the echelle grating determines the spectrum format along the dispersion direction. Blaze wavelengths and free spectral ranges are given in Section . An inclination angle of 0.4 degrees (nominal value) provides a standard format in which blaze wavelengths are located near the center of the detector.

Since the free spectral ranges for near infrared regions (>7200Å) are not covered by the detector, the inclination angle must be set for the appropriate spectrum format.