Once dispersed by the echelle, light in UHRF passes back through the collimator
again and converges as it returns towards the slicer, with a beam
separation of 2
. A secondary
collimator recollimates the beam at a smaller diameter, onto grating cross
dispersers. There is a choice of four gratings
blazed for different wavebands:
U (2400 lines mm
),
B (1800 lines mm
),
V (1200 lines mm
), and
R (1200 lines mm
).