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L-eXtreme Filter 2"


A dual band filter for Astrophotography

L-eXtreme is a two 7nm bandpass filter which can be used with one-shot color cameras like DSLR's (digital SLR), and monochrome CCD cameras. It is also more suited for fast systems. The convenience and cost effectiveness of this filter allows amateurs to image rich emission nebula, even in bright, light pollution skies. It isolates the H-Alpha, and Oxygen III nebula emission lines so that the contrast and signal-to-noise ratio between nebulae are maximized. For people who are living in very light polluted areas, or when the moon is out, the L-eXtreme will be a great filter.

The advantage of the L-eXtreme filter is that there is no transmission between the H-beta and OIII lines, as there is no nebula emission lines there. In this case, it isn't letting light pollution come through so that maximize nebulas signal and make the sky background darker while imaging. The L-eXtreme filter should better isolate the emission lines only and better protect from light pollution

Unlike the Optolong L-eNhance filter which is a tri-band (transmits Hb, Ha, and OIII), the L-eXtreme filter is dual band that passes Ha and OIII emission lines.

Spectral Curve
Technical Data
Substrate: B270
Thickness: 1.85mm
FWHM: O3 7nm+Ha 7nm
Blocking Range: 300-1000nm
Blocking Depth: light pollution lines blocked >99.9%
Surface Quality: 60/40
Transmitted Wavefront RMS: λ/4
Parallelism: 30"




  • Schott substrate material
  • Thickness 2.0mm
  • Surface Quality: 60/40 (Refer to MIL-O-13830)
  • Fine-optically polished to ensure accurate 1/4 wavefront and <30 seconds parallelism over the both surfaces
  • 95% transmission at passband
  • Infrared wavelength 700-1100nm cut-off
  • Precision off-band blocking

Coating Parameter

  • Multi-layers anti-reflection coating
  • Non-cementing optical substrate coating
  • Electron-beam gun evaporation with Ion-assisted deposition coating technology for durability and resistance to scratching, as well as stability on CWL (central wavelength) no deviation affected by temperature change
  • Planetary rotation system offers precision and homogeneity of coatings ensuring high value on transmission of pass-band and Optical density of off-band

Filter Cell

  • Ultra-thin filter cell minimize vignetting by maximize possible clear aperture. Clear aperture is 26mm.
  • Aerometal Material
This item is normally shipped by Courier.