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- Separation of the specroscopic beams from the photometric beams.
- Spectral analysis at three different resolving power values, by the means
of selecting either a prism (LR mode, R=30), a medium resolution
grism (MR mode, R=1500), or a high resolution grism (HR mode, R=12000).
- Formation of the images on the detector plane.
All these functions are accomplished in the spectral range which covers the
astronomical red / near-infrared bands J, H, and, K
1.05 to 2.4 µm). The optics and the support structure are
contained in a vacuum tight cryostat which allows the cooling of the
whole spectrograph to the working temperature of about 77K by means of liquid
nitrogen at atmospheric pressure.
An indepth description with designs and drawings of the AMBER
Spectrograph (SPG) can be found at: AMBER
SPG web-site at ARCETRI