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
Observatories Near-Infrared Filter Set with the following
- 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
- 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.
wavelengths, isophotal frequencies, and flux densities for Vega
For more info check:
- The Mauna Kea Observatories Near-Infrared Filter Set. I. Defining
Optimal 1-5 Micron Bandpasses
D.A. Simons and A. Tokunaga, 2002, PASP
- The Mauna Kea Observatories Near-Infrared Filter Set.
II. Specifications for a New JHKL'M' Filter Set for Infrared Astronomy,
A.T. Tokunaga, 2002, PASP 114, 180
- The Mauna Kea Observatories Near-Infrared Filter Set. III. Isophotal Wavelengths and Absolute Calibration,
and W.D. Vacca, 2005, PASP 117, 421
- Tokunaga's web page.