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Astrodon 5 nm SII Narrowband Filter - 31 mm Unthreaded Insert - SII5-31R

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SKU: ASD-SII5-31R
 

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 5 nm Narrowband Filter Highlights

  • Guaranteed 90%+ maximum transmission for the highest achievable performance
  • 5 nm bandwidth
  • 31 mm unthreaded
  • >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 5 nm SII 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

Setting a new standard for imaging and research performance and durability, Astrodon narrow 5 nm and 3 nm bandwidth filters reduce background noise to enable enhanced contrast of emission objects. Transmittance is guaranteed to be above 90% at the emission wavelength for the highest signal available. The combination of this guarantee and filters with such spectrally narrow bandwidth assures the highest contrast possible. In fact, Astrodon's latest narrowband filters are known to attain 95-98% transmittance. Even when capturing extended 30-45 minute exposures typical of narrowband astrophotography, Astrodon Narrowband filters are still able to minimize halos around bright stars, a skill these filters are known for. Lastly, these Narrowband filters from Astrodon are edge-blackened and feature coatings to the edge of the part. This is integral to keeping the stray light as low as possible for a filter that blocks most light not in the narrow bandpass.

The enhanced contrast these Astrodon Narrowband filters provide is their most distinguishing trait. With improved contrast, faint detail in emission line objects like planetary nebulae and supernova remnants becomes more apparent. This effect is even more pronounced with narrower bandwidth filters. With a filter that's spectrally narrower, however, the difficult part is maintaining a constant signal (% transmission at the emission line). This is why Astrodon's >90%T guarantee is so important as it provides assurance that you'll be able to take advantage of the upgrade in contrast these narrow bandwidth filters offer.