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Filter and Window Changes; Implementation of an Occulting Bar

24 January 2008

Filter Red Leaks Fixed

The problems discussed in the 5 March 2005 Hot News concerning the red leaks in the Si-3 9.7 um and Si-4 10.4 um filters have been fixed. The old BaF2 blocking elements were replaced in November 2005 with CaF2 elements and have since been shown to be reliable in removing any light leaks.

New ZnSe Window for 10 micron Observations

In March 2006, a ZnSe window replaced the coated KBr window in the T-ReCS window wheel. This window has been shown to be more transmissive throughout the 10 micron atmospheric window than the older coated KBr window. It has now become the default window for 10 micron imaging and spectroscopic observations.

New N' Filter

In August 2006 a new N' filter was installed in the T-ReCS filter wheel. This filter is identical to the N' filter used in Michelle at Gemini North. This filter takes advantage of the cleanest, most transmissive parts of the 10 micron atmospheric window, and is expected to be the most sensitive filter available for T-ReCS in this wavelength range. We encourage PIs with challenging imaging programs to consider using this filter in the future.UPDATE 24 January 2008 - Observational tests using the N' filter in T-ReCS have shown an intermittent yet persistent noise pattern that adversely affects the data. Therefore it is recommended that PI's use the N(broad 10um) or Si-5 (11.7um) filter instead at this time.

Occulting Bar Available in Imaging Mode

We fitted T-ReCS with an occulting bar in March 2006. This occulting bar runs vertically through the array and measures 2 arcsec in width. The newest PIT and OT software available starting 2007A will have the ability to choose the occulting bar in an imaging observation. More details will be available on the T-ReCS webpages soon.

Last updated 2008 January 24; James Radomski