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UIST Engineering

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UIST: Engineering: Filter Wheels

UIST logo

UIST has two 24-slot filter wheels which contain filters for both imaging and for blocking the spectroscopy grisms. The MKO consortium filter set is installed where possible (see the discussion of new JHK standards for example). Click on the filter name to see an image of the profile (where available). Text files are also available giving transmission profiles for some of the filters, contact Watson Varricatt. The table below lists the filter wheels' population.

The "black blank" is used for darks. This mask is painted with NEXTEL. The other "blanks" in the wheels are uncoated aluminium.

NOTE: Filters are grouped together to avoid leaks from adjacent filters. So in other words, we avoid putting short-wavelength filters next to thermal filters. (However, tests using two blanks in slots 22, which were next to the Mp and M-spectral filters in slots 21, gave near-normal dark current of ~1.0 e-/sec in 100-second exposures.)

9 January 2007 -
Wheel 1 Wheel 2
Posn Filter 50% Cut on 50% Cut off Step val. Posn Filter 50% Cut on 50% Cut off Step val.
1 Open - - 14,700 1 Open - - 78,100
2 Blank - - . 2 9.95mm circ aper - - .
3 Black blank - - 7,374 3 IJH blocker 0.90 1.82 .
4 Y[MK] 0.966 1.072 3,707 4 B2 blocker 1.43 2.60 .
5 Hartmann mask - - 40 5 J-spectral 0.96 1.71 .
6 Z[MK] 1.008 1.058 84,373 6 HK-spectral 1.58 3.38 .
7 K_s_MK 1.990 2.310 80,706 7 H-spectral 1.27 2.50 .
8 Klong 2.019 2.434 77,039 8 KL-spectral 2.11 3.13 .
9 1.57(cont)[MK] 1.561 1.583 . 9 L-spectral 2.56 4.61 .
10 FeII[MK] 1.630 1.656 . 10 J[MK] 1.17 1.33 45,105
11 2.248(S1) 2.234 2.269 . 11 H[MK] 1.49 1.78 41,438
12 2.248 MK 2.235 2.270 . 12 K[MK] 2.03 2.37 37,771
13 2.122(S1) 2.106 2.124 . 13 3.4nbL 3.379 3.451 .
14 2.122 MK 2.103 2.134 . 14 3.5mbL 3.383 3.594 .
15 BrG MK 2.150 2.182 . 15 3.6nbLp 3.560 3.625 .
16 CH4_s 1.550 1.657 . 16 3.99(cont) 3.964 4.016 .
17 CH4_l 1.617 1.730 . 17 BrA 4.025 4.080 19,436
18 2.27cont[98] 2.257 2.291 . 18 PAH MK 3.264 3.318 .
19 2.42CO 2.413 2.436 . 19 3.28"Dust" 3.250 3.305 .
20 L'[MK] 3.428 4.108 . 20 3.05ice MK 2.970 3.125 .
21 M'[MK] 4.572 4.800 . 21 M-spectral 3.5 6.0 4,768
22 blank -- -- 25,701 22 Blank - - 1,101
23 PK50 2mm -- 2.7 22,034 23 PK50 2mm -- 2.7 85,434
24 Blank - - 18,267 24 blank - - 81,767

Wheel Movement
Both wheels move in either direction. Consequently, if a required filter step value is greater than the current value, the wheel will move through increasing steps; if the required filter is at a lower step value, the wheel steps will decrease. This means that moving from Posn. 3 (the "black blank") to any other filter in wheel 1 would move through the open position. Likewise, moving back to blank would move through the open position.

History
15 Dec 2008: PK50 filter is now added in combination with the "Y_MK" filter since the "Y_MK" is found to have a red leak.
15 July 2008: PK50 filter is now added in combination with the "K_s_MK" filter since the "K_s_MK" is found to have a red leak.
9 January 2007: Replaced two blank filters with Y-band and IJH spectral blocker (for use with the IJ and JH grisms).
11 July 2006: The "Kshort" filter is replaced with a "K_s_MK" Mauna Kea Consortium filter. The existing PK50 filter is replaced with a new one (with the same specifications).

Previous filter wheel arrangement is available here.


Contact: Chris Davis. Updated: Tue Dec 16 10:09:59 HST 2008

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