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Astrodon 5 nm Red Continuum Narrowband Filter - 49.7 mm Round Unmounted - REDCON5-50R

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SKU: ASD-REDCON5-50R

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 Narrowband Filter Highlights

  • Guaranteed 90%+ maximum transmission for the highest achievable performance
  • Filters come in 5 nm bandwidth for general use, as well as 3 nm bandwidth for maximum contrast and blocking of moonlight and light pollution
  • >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 Narrowband Filters - Additional Information

The most noteworthy feature of Narrowband filters is their capacity to enhance the contrast of objects in the emission line by accepting only a narrow range of wavelengths near the hydrogen H-Alpha, oxygen OIII, sulfur SII (656 nm, 501 nm, and 672 nm respectively), and other emission lines.

Astrodon filters are suitable for use in locations with heavy light pollution, as well as with the Moon out for longer imaging sessions.

FWHM, or full-width at half-maximum, intensity is used to define the narrow scope of Astrodon filter wavelengths. Although background signal is minimized when narrower filters are used, sustaining a high transmission through the filter bandpass as it gets narrower can be a challenge. If maximum transmission diminishes as the filter becomes more narrow, the emission signal also diminishes and S/N (signal-to-noise) gain will not be achieved. This high transmission objective for narrowband filters has been realized by Astrodon.

Astrodon's narrowband filter line has evolved from 6 nm to 5 nm FWHM and now also includes the ultra-narrow 3 nm FWHM for H-Alpha, OIII, and SII, as well as a 5 nm Red Continuum filter (645 nm) that produces a star map without hydrogen-alpha or sulfur II emission in order to subtract stars from emission images. Astrodon Narrowband filters are renowned for generating a deficiency in halos around stars and for not leaking NIR light.

Main image may not depict the exact filter you will receive.