Radian Triad Ultra Narrowband Filter 1.25"- For Fast Telescopes

Brand: Radian


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  • Designed to be 1.5nm shifted to the red
  • Filter size: 1.25-inch
  • Designed for telescopes f/3 and faster

Product Details

  • You asked, and we listened: the Triad Ultra is now optimized for today's fast focal ratio telescopes! Owners of fast telescopes let us know that the broad light cone of fast telescopes prevented some light from reaching the sensor through the original Triad Ultra. We're happy to announce that this pre-shifted version of the Triad Ultra is now optimized for telescopes!

    Use Case for Full-Spectrum Color Cameras

    The Triad Ultra filter stands alone in its class as a filter with four ultra-narrow bandpasses that cover Hydrogen alpha, Hydrogen beta, Sulfur II, and Oxygen III wavelengths - the four most common wavelengths for narrowband astrophotography. As a multi-narrowband filter, the Triad Ultra is designed to photograph emission nebulae, planetary nebulae, and supernova remnants, and excels at doing so from light pollution. However, we recommend you try it from dark skies as well - the narrow bandpasses will give you tighter stars and more pronounced nebulosity.

    Use Case for Monochrome Cameras

    You might think that the Triad Ultra is only designed for color cameras, but it actually works great on monochrome cameras too! A traditional luminance filter has a broad bandpass that lets light in from around 400 to 700nm. This works well for broadband imaging of galaxies and reflection nebulae, for example, but will be affected heavily by light pollution with such a broad bandpass. With the Triad Ultra, you can gather luminance data in all four major wavelengths while simultaneously cutting out light pollution and you get the added benefit of keeping the stars tight and small. Think of it as the ultimate luminance filter for your monochrome camera!

    Optimized for f/3 Optical Systems

    With the Pre-Shifted Triad Ultra, the f/3 beam has a 9.5-degree half cone angle. Filters with bands this narrow shift 1.5nm to the blue. This causes the transmission at the lines of interest to get reduced. The Pre-Shifted Triad Ultra is designed to be 1.5nm shifted to the red, so that in the f/3 beam they are adjusted perfectly. This specially-optimized Triad Ultra for fast  telescopes around f/3 will provide significantly better performance at ultra-fast focal ratios than the original Triad Ultra. Below you'll see a spectra that shows the Pre-Shifted Triad Filter's calculated for performance with an f/3 light cone:

    Radian Triad Ultra Pre-Shifted f/3 Spectral Response Graph


    The Triad Ultra is 100% American made and uses advanced multi-coatings and extreme tolerance glass, to ensure it is always consistent and accurate. Filter thickness is 3mm. Below you'll see an incredible image of the Cave Nebula taken by Drew Evans using the Pre-Shifted Triad Ultra filter:


    Shop the full Radian Triad Filter Lineup

  • specifications

    Filter ShapeRound
    Filter Thickness3mm
    Filter TypeLight Pollution/City Light Suppression
    Filter TypeTriad
    Free ShippingYes
  • included items

    • 1.25-inch Pre-Shifted Triad Ultra Filter
    • Filter case


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