Science Operations

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.

Order Sorting Filters: The order sorting filters are identical for the 2 LUCI’s.

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.