WIRC Filter Transmission Profiles

Note: This page is a recreation of the original page from the University of Virginia, which is now defunct.

Filters available for use in WIRC are listed below. The filters are used at approximately 77K and 7 degrees angle of incidence (AOI).  Most of the manufacturer's provided transmission profiles are for 300K and 0 degrees AOI.  Both the temperature and tilt cause a shift of the filter transmission profile blueward.  Corrections for these effects have been applied to the manufacturer's supplied data where possible.

Broadband Filters

Filter Scanned Data Original Data Tilt Corrected Data Temperature Shift (298 to 77K) Manufacturer Note
J J Graph OCLI 1
K H Graph OCLI 1
Ks Ks Graph
K Blocking
Ks Original
Ks Tilt
cut-on: -0.6 nm
cut-off: - 0.2 nm


Narrowband Filters

Filter Scanned Zoomed Profile Original Data (3) Temperature & Tilt Corrected Data (4,5) Manufacturer
J-Cont J-Cont Zoomed Graph J-Cont Original J -Cont Temp & Tilt NDC
Pa-Beta Pa-Beta Zoomed Graph Pa-Bata Original Pa-Beta Temp & Tilt NDC
H-Cont H-Cont Zoomed Graph H-Cont Original H-Cont Temp & Tilt NDC
Fe-II Fe-II Zoomed Graph Fe-II Original Fe-II Temp & Tilt NDC
Br-Gamma Br-Gamma Zoomed Graph Br-Gamma Original Br-Gamma Temp & Tilt NDC
K-Cont K-Cont Zoomed Graph K-Cont Original K-Cont Temp & Tilt NDC
CO(2-O BH) CO(2-O BH) Zoomed Graph CO(2-O BH) Original CO(2-O BH) Temp & Tilt NDC


Methane Filters

Filter Scanned Zoomed Profile Original Data Tilt Corrected Data Temperature Shift Manufacturer Note
CH4 L Zoomed Graph
CH4 L Original
CH4 L Tilt
cut-on: - 13.9536 nm
cut-off: - 12.8952 nm
CH4 S Zoomed Graph
CH4 S Original
CH4 S Tilt
cut-on: - 13.9536 nm
cut-off: - 13.176 nm


(1) The following values are taken from the side of the filter boxes.  Although they do not match the scanned data, the graphs are representative of standard H and K transmission.

J Filter H Filter
SO 14-8744-460 14-8744-460
PO 393 745 393 745
RN 1011-534Z/541Z 563-606/607
SN 33   41
LOT 4Z 7


(2) AOI for original data is 5 degrees.

(3) Original Data taken at 300K and 0 angle of incidence.

(4)  Wavelength shifts due to temperature were derived using center wavelength v. temperature data for a sample as measured by the manufacturer (see plots below).  The difference between the peak temperature (300K for narrowband filters, 293K for methane filters) and the operational temperature of 77K was taken to establish a delta wavelength.  This value was then subtracted from the reported wavelengths in the original data to establish the working wavelengths at 77K.  

(5)  Wavelength shifts due to filter tilt were made according to Ghinassi, F. et al.(A&A 386, 1157. 2002).  The degree of tilt was taken to be 7 degrees, and the filter index of refraction was estimated to be 2, as recommended in the paper.

(6) Two equations were given for temperature corrections.

More Scanned Data

Plots from NDC  

Percent Transmittence vs. Wavelength(nm)

Filter Full Continuum Profile Temp Shift w/Temp
J-Cont J-Cont Full Graph J-Cont Graph
Pa-Beta Pa-Beta Full Graph Pa-Beta Graph
H-Cont H-Cont Full Graph H-Cont Graph
Fe-II Fe-II Full Graph Fe-II Graph
Br-Gamma Br-Gamma Full Graph Br-Gamma Graph
K-Cont K-Cont Full Graph K-Cont Graph
CO(2-O BH) CO(2-O BH) Full Graph CO(2-O BH) Graph
CH4_L CH4_L Full Graph CH4_L Graph
CH4_S CH4_S Full Graph CH4_S Graph


Created by CMH, March 15, 2017