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Astrodon 3 nm H-Alpha Narrowband Filter - 65 mm Square Unmounted - HA3-65S

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SKU: ASD-HA3-65S

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 H-Alpha Narrowband Filters

Highly favored among narrowband filters, hydrogen-alpha filters for 656 nm are deep red in color. As it is the most common element in the universe, hydrogen is present in emission nebula such as the North American and the Pelican, planetary nebula such as the Dumbbell and Ring, Wolf-Rayet objects like Cresecent and Thor's Helmet, as well as supernova remnants like the Veil nebula. While many imagers are content to dsiplay a simple black and white h-alpha image of an object, most imagers will want to combine their h-alpha data with their red RGB data in order to augment structural detail while preserving a "natural" appearance. For this reason, h-alpha filters make a perfect initial narrowband extension of your LRGB filters.

Astrodon Narrowband Filters - Additional Information

Setting a new standard for imaging and research performance and durability, Astrodon narrow 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.