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The original FLAMINGOS J, H, Ks and K filters were fabricated by OCLI as part of a consortium purchase and were loaned from NOAO. In 2003, the J, H, and Ks filters were replaced by Barr filters, which have similar, but not identical, characteristics. Barr provided wavelength scans at both ambient (300 K) and cryogenic (77 K) temperatures. The OCLI K filter had been provided with only cryogenic tracings. The spectroscopic order separator JH and HK filters were later purchased from Janos, but were scanned only at ambient temperature. In May 2008, all of the filters were removed as part of maintenance on the mechanism and traced on the NOAO Lambda-9 spectrometer at ambient temperature. These results are summarized on the filter plots on the following links, which are color coded black (vendor ambient temperature), red (vendor cryogenic temperature), and green (NOAO ambient temperature). The small offset between the NOAO and vendor ambient plots may represent a suspected offset in the Lambda-9 zero point and not a real shift in the filter properties. Only the NOAO ambient plots are provided for the JH and HK filters, since they were never scanned at cryogenic temperatures.
As noted in the Hot News, the K filter has been removed from FLAMINGOS and replaced with a multiband low-background J filter obtained from James Rhoads as part of an experiment in the fabrication of filters with multiple custom transmission windows to minimize the OH background. Imaging and spectroscopic tests were carried out in October 2012, but unless there is demand for the K filter or James requests the return of the JLo filter, it will remain until there is an independent need to open up the camera dewar because of the effort required to do so.
NOTE: The K filter has been removed from FLAMINGOS. The JLo filter has five bandpass windows within the 1.09 - 1.385 μm range.