Optolong 1.25" L-eXtreme Dual Band 7nm HA/OIII Filter - LXT-125

Article number: LXT-125
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The 1.25" L-eXtreme Dual Band filter from Optolong is a 7nm bandpass filter suited or fast systems and one-shot color cameras and monochrome CCD cameras. Optolong has ensured that the L-eXtreme filters do not transmit between H-beta and OIII lines, as there are no nebula lines there. Limiting the transmission this way means that light pollution is blocked so nebula signals are boosted and the background of the sky becomes darker for better contrast during imaging. This is an excellent filter for those who live in areas with higher light pollution emissions or those who would like to image when the Moon is bright.

This Optolong L-eXtreme threaded filter isolates the H-Alpha and Oxygen III emission lines in order to maximize the signal-to-noise ratio between nebulae. When compared to the Optolong L-eNhance tri-band filter, the dual band only emits the Ha and OIII emission lines rather than the L-eNhance filters transmission of Hb, Ha, and OIII.

During manufacturing, Optolong uses high-precision grinding and polishing to ensure that the substrate parallelism is greater than 30" and the surface accuracy is better than λ/4. Electron-beam gun evaporation and Ion-assisted deposition (IAD) coating is applied to provide durability and resistance to scratching. This technology also provides stability on the central wavelength so there is no deviation during temperature changes. IAD increases film firmness, consolidates membrane compactness, and changes vacuum coating material characteristics. After manufactured, each filter is examined by Spectrophotometer and Laser Interferometer for spectrum characteristics and surface accuracy respectively.


L-eXtreme Dual Band Filter Specifications



  • Substrate: B270
  • Filter Size: 1.25"
  • Thickness: 1.85mm
  • FWHM: OIII 7nm+Ha 7nm
  • Blocking range: 300-1000nm
  • Blocking depth: light pollution line blocking >99%
  • Surface quality: 60/40
  • Transmitted Wavefront RMS: λ/4
  • Parallelism: 30s
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