The IDAS Oxygen III filter is designed to isolate the OIII emission bands for best signal-to-noise performance for a wide range of telescope designs.

Features include:

• 6.0 +/- 0.2nm (Measured value)
• 98% transmission rate (Measured value)
• Flat top, which maximizes the transmission even for fast optics
• Out-of-band blocking: 300-1300nm
• Configurations:
  • 2.5mm or 3.0mm thickness options
  • 3 mount sizes - 48mm, 52mm & 50.8 (for filter wheels)
• Each filter is individually inspected for quality. The filter response is plotted and provided with each unit.
• Made in Japan

Filter Plots:

Click on the plots to see an enlarged view.

The plots below show the different filter performance with various astrograph designs - refractors vs. telescopes with central obstructions. Note that the nominal response of the filter shifts when considering all angles of incidence to the filter surface caused by the objective's f-ratio, but the filter response is designed to compensate in fast, obstructed optics by picking up more of the shorter wavelength component of the OIII emission line pair. The OIII emissions consist of lines at 495.9 and 500.7 nm, with the shorter wavelength intensity at 40% of the longer wavelength as noted on the plots.