Narrowband OIII 18nm Light Pollution Filter - Ideal for Nebula Observation

The Optolong narrowband OIII filter is designed for nebula observation allowing 18nm bandwidth of light centered on a wavelength of 500nm through, which corresponds to OIII emission lines, and reducing the transmission of certain wavelengths of light, specifically those produced by artificial light including mercury vapour, and both high and low pressure sodium vapour lights and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. skyglow).

OIII emits 495.9nm and 500.7nm and it is a blue-green coloured filter. Many images of planetary nebula and supernova remnants are taken only with H-alpha and OIII filters. They show great structural details, but have natural colours, looking like an RGB image.

Warning - Optolong filters are not designed to be used for solar observation. Do not look at the sun through this filter as it will cause permanent eye damage.

FEATURES

• 90% transmission at major OIII line 495.9nm and 500.7nm.
• 0.1% transmission of off-band, specifically the major emission lines of artificial light pollution (i.e. Na 589nm, Hg 435nm and 578nm)
• Suitable for visual observations on most emission nebulae, planetary nebulae and supernova remnants
• 1.25' or 2' Mounted Sizes.
• Supplied in a protective plastic case with EVA foam lining
• 2mm (1.25' / 2') Thick Schott Glass
• Fine-optically polished on both sides - ensures accurate λ/4 wavefront and <30 seconds parallelism over the both surfaces
  
  

  Please note - this graph is for the older generation which had a 25nm bandwidth. This updated 18nm version has a tighter bandpass area.

  Red Line - Represents the transmission curve of the OIII Filter.

  Green Line - The Major Emission Lines of Nebulae: H-α (656.3nm), H-β (486.1nm), OIII (495.9nm) and OIII (500.7nm)

  Orange Line - The Major Emission Lines of Artificial Light Pollution: Hg / Mercury (435.8nm, 546.1nm, 577nm and 578.1nm), Na / Sodium (598nm, 589.6nm, 615.4nm and 616.1nm)