The Canadian Telescopes Oxygen III is among the best very narrow bandpass Nebula Filters. These are often referred to as light pollution rejection filters but their effect is more encompassing than that alone. This Oxygen III filter is a genuine bandpass filter made so that only a small portion of light in the visual doubly ionized Oxygen III portion of the spectrum is transmitted. This filter will pass only six (6) nanometer half width centered at 496 and 501 nm Oxygen III lines, with transmission of ninety three (93) per cent of that light in the portions of the spectrum commonly emitted by diffuse and emission nebula (the Veil, North American, or Dumbell Nebula for example), and planetary nebulae (Ring Nebula for example). By rejecting most other light this will cause certain nebula appear more clearly against a blacker background of space.

The glass elements used to make the Canadian Telescopes are free of striae, optically finely polished plane parallel to within 30 seconds of arc. This eliminates any double images or ghosting due to wedge errors in the glass. The thin 1.5 mm profile allows these filters to be inserted anywhere into the optical path without introducing.

Each filter cell incorporates both a male and a female thread to allow stacking the filters to obtain even narrower pass bands or special effects.

•   Since the transmission of the light in the OIII is so efficient, fainter nebula seem to appear brighter and the extent of nebulosity that can be seen is greater - you will see more of the fainter components. 


•   Since the transmission of the other regions is so limited the background appears blacker, hence what is visible is more clearly contrasted against its background. 


Stars appear more natural, smaller, and more intense - stars are not bloated or halted by this filter. No image degradation is perceptible even at the highest magnifications.

This filter has been designed for Canadian Telescopes in Canada and are made in Japan.