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| Joint Astronomy Centre |
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UIST has two 9-slot grism wheels which contain the polarimetry prism
and the grisms for spectroscopy. The table below lists the grism
wheels' population. See the UIST filter-wheels web page for
cut-on/cut-off wavelengths for the filters. Note that the
short-/long- grisms are used in second order, so some ofthe blocking
filter choices are driven by the need to block different orders
(e.g. 2nd order lines between 1.34-1.51 passed by the B2 would appear
in the short-K grism in 3rd order [at 2.00-2.26], so the short-K cutoff
must be >1.51um; similarly, 2nd order lines between 1.58-1.67 would
come through the HK filter and be seen by long-K in 3rd order
[at 2.37-2.51], so the long-K blocker cut-off must be >1.67um).
*Used with the HK cross-disperser (so no need for blocking) Movement between positions 5 or 6 and the other positions involves moving passed a datum switch. Previous grism wheel arrangements: Pre-20030301.
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