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).
1 March 2003 — 9 March 2004
|Wheel 1||Wheel 2|
|2||Short J||54||242.4||J-spectral||2||HK low*||84||169.7||non|
|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|
*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.