The MTR2 is made of a predispersor (“SP1” first one on the left part), forming a lowres spectrum on the wavelength selector (so called the “mask plate”). From there, only the selected bandwiths travel to the highres echelle spectrograph (right part), ending over the MTR cameras at the SP2 output (one bandwith per camera).

The optical layout along Y is fixed (no changes, never). The ruling of the gratings are along Y only and the dispersion of both spectra is along Z only. The entrance slit is fixed (but for its width), and such are the collimators and camera mirrors.

The moving parts are:

• The predisperser gratings selection table (EM35). There are 3 selectable predispersers, although only one (the central slot) is mainly used for MTR2 operation.
• PThe predisperser rotates about the Y axis to change its grating incidence angle (EM37). This allows shifting the lowres spectrum along Z over the masks stop plate.
• The mask plate translates in the Z direction (EM39)

  • The echelle grating rotates about the Y axis to change its grating incidence angle a (EM32). This allows shifting the highres spectrum along Z at the SP2 output.
• The legacy “DPSM engage” mirror (EM71, “out” in normal operation.
• Each of the 4 spectrograph mirrors has a mechanical shutter (EM50 to EM53)

In short:

1. The main optical layout (F2 to SP2) is static and does not require changes for daily operation.
2. Spectral confguration of the multiline is obtained using:

   • both gratings rotation
   • masks plate tuning in translation
   • manual setup of the spectral cameras at the SP2 output

Data and formulae for the MTR2 can be found in the following document:
THEMIS spectrograph (auth: CLM)

These tools allow the observer to quick check the feasibility of a setup

• MTR spectrograph simulator (java web version / auth: CLM)
• MTR spectrograph simulator (Downloadable excel version / auth: CLM)
  Please enable macros to get a correct result.

• Solar spectrum (3800 to 8700 A with identified lines)
• Solar lines (2935 to 8770 A, Moore & Minaert (M&M), NIST)
• Solar spectrum (BASS2000 interactive plot)
• Solar spectrum (Astrosurf: interactive 2d with M&M identification)