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Astrodon 3 nm OIII Narrowband Filter - 65 mm Square Unmounted - OIII3-65S

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About Astrodon Narrowband Filters

Astrodon filters are high performing, durable filters that provide significant aid for astrophotography and research pursuits. Each filter is constructed using a highly innovative process with a single high quality 3 mm thick fused silica substrate and full hard oxide sputtered coatings. With these Astrodon Narrowband filters, imagers can count on consistently high performance, as well as a more narrow spectrum compared to most other filters for superb contrast and the ability to view the faintest nebula detail. Astrodon guarantees >90%T performance at the emission line.

Astrodon 3 nm Narrowband Filter Highlights

  • Guaranteed 90%+ maximum transmission for the highest achieveable performance
  • 3 nm bandwidth
  • >OD 4 (0.01% transmission) out-of-band blocking
  • Clear 1/4 wave substrates feature hard-oxide coatings to the edge, removing light leakage from uncoated rims
  • Edge blackened to reduce reflections
  • Parfocal with all other filters made by Astrodon.

Astrodon 3 nm OIII Narrowband Filters

Following the additions of the H-Alpha and OIII filters, the next filter you'll need to add to your collection is the SII or Sulfur II filter, especially if you want to view Hubble Space Telescope (HST) images like the popular "Pillars of Creation" (Eagle Nebula, Messier 16). Like the H-Alpha filter, the SII filter also has a deep red color close to 672 nm. For many emission nebulae, H-Alpha, OIII, and SII filters all give you that Hubble look. Tri-color narrowband imaging using these three filters is possible with the Moon up so your imaging gear doesn't have to be sidelined for weeks at a time.

Astrodon Narrowband Filters - Additional Information

Astrodon Narrowband filters set a new standard for imaging and research performance and durability. These filters enhance contrast in emission line objects via narrow 5 nm and 3 nm bandwidths. With a transmittance guaranteed to be above 90% at the emission wavelength, these filters offers the highest signal available. This guarantee combined with a spectrally narrow bandwidth ensures maximum contrast. As a matter of fact, the latest narrowband filters from Astrodon typically achieve a transmittance of between 95 and 98%. Even when taking exposures common to narrowband astrophotography, typically 30-45 minutes in length, these Astrodon Narrowband filters still have the ability to keep halos around bright stars at a minimum, a feature for which these filters are renowned. Finally, these filters are edge-blackened with hard-oxide coatings from edge to edge to eliminate the chance that an uncoated border will cause light leakage. This is critical to keeping stray light to a minimum for a filter that blocks all light save for the narrow bandpass.
With Astrodon Narrowband filters, it's all about the enhanced contrast. The better the contrast, the more the fainter characteristics of celestial objects are highlighted. This improves with filters that have narrower bandwidths. However, maintaining a constant signal (%T at the emission line) as the filter gets spectrally narrower can be difficult. This is what makes Astrodon's >90%T guarantee so critical as it assures that you'll be able to benefit from the enhanced contrast provided by narrower filters.