Filters
Each instrument has two 15-position filter wheels. The two LUCIs are currently equipped with a nearly identical set of 19 science filters, including broad- and narrow-band filters and a couple order-sorting filters for the low-resolution grating. The central wavelength, FWHM, peak and mean transmissions are listed for both instruments in the table below. Plots of their transmission curves are also shown.
| Filter Name | Filter Wheel | LUCI1 | LUCI2 | ||||||
|---|---|---|---|---|---|---|---|---|---|
| λc [µm] |
FWHM [µm] |
τpeak [%] |
τave [%] |
λc [µm] | FWHM [µm] |
τpeak [%] |
τave [%] |
||
| z (1) | 2 | 0.957 | 0.195 | 98.4 | 94.3 | 0.965 | 0.196 | 93.8 | 89.9 |
| J | 2 | 1.247 | 0.305 | 91.2 | 83.2 | 1.250 | 0.301 | 90.9 | 87.1 |
| H | 2 | 1.653 | 0.301 | 95.0 | 90.5 | 1.651 | 0.291 | 92.1 | 85.4 |
| K | 2 | 2.194 | 0.408 | 90.1 | 85.7 | 2.199 | 0.408 | 92.1 | 84.5 |
| Ks | 2 | 2.163 | 0.270 | 90.7 | 86.8 | 2.161 | 0.270 | 91.7 | 85.9 |
| zJspec | 2 | 1.175 | 0.405 | 93.1 | 90.4 | 1.175 | 0.405 | 93.1 | 90.4 |
| HKspec | 2 | 1.950 | 0.981 | 95.0 | 86.3 | 1.953 | 0.998 | 95.7 | 88.3 |
| Y1 | 1 | 1.007 | 0.069 | 67.3 | 65.2 | 1.007 | 0.069 | 67.3 | 65.2 |
| Y2 | 1 | 1.074 | 0.065 | 94.2 | 92.8 | 1.074 | 0.065 | 94.2 | 92.8 |
| OH_1060 | 1 | 1.065 | 0.010 | 68.6 | 65.2 | 1.065 | 0.010 | 68.6 | 65.2 |
| OH_1190 | 1 | 1.194 | 0.010 | 80.4 | 78.6 | 1.194 | 0.010 | 80.4 | 78.6 |
| HeI | 1 | 1.088 | 0.015 | 65.2 | 64.6 | 1.088 | 0.015 | 65.2 | 64.6 |
| P_gamma | 1 | 1.097 | 0.010 | 81.1 | 80.0 | 1.096 | 0.010 | 70.4 | 68.9 |
| P_beta | 1 | 1.283 | 0.012 | 86.1 | 85.5 | 1.284 | 0.013 | 85.8 | 85.2 |
| J_low | 1 | 1.199 | 0.112 | 95.4 | 93.5 | 1.199 | 0.112 | 95.4 | 93.5 |
| J_high | 1 | 1.303 | 0.108 | 95.3 | 93.2 | 1.303 | 0.108 | 95.3 | 93.2 |
| FeII | 1 | 1.646 | 0.018 | 91.2 | 89.5 | 1.645 | 0.018 | 91.1 | 88.0 |
| H2 | 1 | 2.124 | 0.023 | 87.9 | 84.9 | 2.127 | 0.023 | 83.9 | 82.0 |
| Br_gramma | 1 | 2.170 | 0.024 | 79.4 | 76.5 | 2.171 | 0.023 | 83.1 | 82.0 |
(1) Note: The dichroic the blue cutoff for the z filter in LUCI2
Each filter wheel contain a clear filter and a blind filter. The clear filters are to maintain approximately the same focus on the detector through all filter combinations. When you request an observation with a specific filter, whether broad or narrow band, you will automatically get a clear filter in the other filter wheel unless crossing filters. The blind filters are aluminum plugs that help block stray light from getting to the detector, such as when taking dark frames.
Transmission Curves
Broadband Filters: In the following, LUCI1 is depicted with a green curve, LUCI2 is depicted with a red curve.
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Order Sorting Filters: The order sorting filters are identical for the 2 LUCI’s.
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Narrowband Filters: The Br_gamma, FeII, H2, P_beta, and P_gamma filters are slightly different between LUCI1 and LUCI2. In the following, LUCI1 is depicted with a green curve, LUCI2 is depicted with a red curve for those filters. The remaining Narrowband filters (Y1, Y2, HeI, OH_1060, OH_1180, J-low, and J_high) are identical between the 2 instruments.
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Tellurics are assumed to be brighter than ~10.5 mag requiring a crossed filter combination. The standard combinations are:
| Filter Wheel 1 | Filter Wheel 2 | Extinction [mag] |
|---|---|---|
| P_gamma | J | 0.8 |
| HeI | J | 2.35 |
| OH_1060 | z | 3.9 |
| HeI | z | 7 |
