UIST has two 9-slot grism wheels which contain the polarimetry prism and the grisms for spectroscopy. The table below lists the grism wheel populations.
FILTERS: 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 of the 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).
WEIGHTS: These are for the grism AND the holder. The holders alone (with screws, clips, etc.) each weigh 124.2g.
REF: The refence number is etched onto the grism and the grism holder. The full reference number is 30a##m, e.g. for the short J the code is 30a54m.
9 March 2004 — 1 May 2005
|Wheel 1||Wheel 2|
|4||Short L||59||217.4||L-spectral||4||HK||83||181.4||B2 (cgs4)|
|8||Long K||55||251.4||KL-spectral||8||Long L||58||235||L-spectral|
Movement between positions 5 or 6 and the other positions involves moving passed a datum switch.
9 March 2004: The new zeiss grisms (below) were found to be faulty (poor throughput). These were removed today for return to Zeiss. Posns 2 and 7 were left vacant (i.e. holder installed but with no grism or blank).
1 March 2003: New HK low and IJ grisms (Zeiss – direct ruled infrarsill) were installed. These replaced hyperfine grisms that were found to be faulty.