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The GEMINI infrared filter consortium

The NOT is participating together with a number of institutes in a group filter purchase of a set of new standardized IR filters named Mauna Kea Observatories Near-Infrared Filter Set with the following specifications:
  • Out of band transmission <10-4 out to 5.6µm.
  • All parameters for 65 K; cold filter scans of witness samples to be provided with prediction of wavelength shift with temperature.
  • 60-70% peak transmission (goal >70%) for narrow-band filters. Bandwidth <= 1.5%.
  • >80% average transmission (goal >90%) for broad-band filters and special filters.
  • Peak transmission level of broad band filters to have a ripple of less than ±5% of average transmission between 80% points.
  • Half-power points ±0.5% for broad-bands; ±0.2% for narrow-bands.
  • Roll-off spec: <2.5% slope for broad-bands; <0.5% for narrow-bands.
  • Substrate flatness prior to coating is /10 Peak-to-Valley at 0.63 µm on a best effort basis.
  • Scratch/Dig: 40/20.
  • Substrate surfaces parallel to 5 arcsec or better.
  • Filter to be designed for a tilt of 5 degrees.
  • Diameter: 60 mm, or cut to requested size. Inner 90% to be useable. After cutting to a smaller size, the filter is useful to the edge.
  • Maximum thickness: 5 mm.
  • No radioactive materials to be used (may cause spurious noise spikes).
  • Filter to be single substrate.

Isophotal wavelengths, isophotal frequencies, and flux densities for Vega
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Back to top Last modified: June 28 2023