Instrument Characteristics
- Guiding and WFS (AGw)
- Calibration Unit
- Dichroic
- Masks
- Grating and Prisms
- Filters
- Shutter
- Detector
- IMCS (Image Motion Compensation System)
The two MODS are identical and are mounted at the straight-through f/15 direct Gregorian foci, directly below each of the LBTO 8.4-m primary mirrors. MODS1 is on the SX (left) side and MODS2 on the DX (right). The guiding and wavefront-sensing systems, as well as the calibration units, are built into the instruments.
MODS is a double channel spectrograph which can be operated in dual-channel mode to cover the spectral range from 3200-10000 Å all at once, or, if the dichroic is replaced by a folding flat (#1 in the diagram below), then all of the light is directed to the red channel for red-only mode (5000-10000 Å), and if instead there is no optic, light passes straight into the blue channel for blue-only mode (3200-6000Å).
The optical layout is shown below. Each channel has its own collimator, dispersers, camera, filters, field flattener (FF) lens which also serves as the dewar window, and detector.
