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Optolong OIII 18nm Nebula Filter
Optolong OIII 18nm Nebula Filter
Optolong OIII 18nm Nebula Filter
Optolong OIII 18nm Nebula Filter
Optolong OIII 18nm Nebula Filter
Optolong OIII 18nm Nebula Filter
Optolong OIII 18nm Nebula Filter

Optolong OIII 18nm Nebula Filter

par Optolong
UGC OPT-12701
CA$111.00 - CA$151.00
CA$111.00
CA$111.00 - CA$151.00
CA$111.00
Égalisation de prix!
  • 18nm Bandpass Centered on OIII Emission Lines (500nm)
  • Greater than 80% Average Light Transmission (Tave)
  • Blocks >99% of Major Light Pollution Lines
  • 1.85mm Thick Optical Glass Substrate
  • λ/4 Transmitted Wavefront and 60/40 Surface Quality
2 en stock
Admissible à la livraison GRATUITE au Canada pour les commandes de plus de 500$.
  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • Optolong OIII 18nm Nebula Filter

    The Optolong OIII 18nm Nebula Filter isolates the critical 500nm emission lines from planetary nebulae and supernova remnants with its focused 18nm bandpass. By achieving over 80% average transmission at these key wavelengths while blocking more than 99% of light pollution within its 400-700nm range, this filter dramatically increases contrast. The optically flat λ/4 wavefront ensures your telescope's resolution is preserved, delivering sharp, high-contrast views even from suburban skies.

    Isolating Nebulae: The 18nm OIII Passband

    This filter is engineered to transmit a specific 18nm sliver of the blue-green spectrum, centered at 500nm. This window precisely captures the light from doubly ionized oxygen (OIII), the primary emission from targets like the Dumbbell Nebula (M27) and the Veil Nebula (NGC 6960). By isolating this light, the filter renders these faint structures visible against a darkened sky background.

    High-Contrast Views from Blocking >99% of Light Pollution

    The core function of the Optolong OIII filter is to improve contrast by aggressively rejecting unwanted light. It blocks over 99% of the primary wavelengths associated with mercury vapor, sodium vapor streetlights, and natural skyglow. This doesn't make the nebula brighter in absolute terms; it darkens the sky so severely that the nebula's faint details stand out in stark relief, transforming a washed-out view into a well-defined object.

    Precision Optics: λ/4 Wavefront and 60/40 Surface Quality

    A filter should only reveal detail, not degrade it. Optolong builds this filter on a 1.85mm optical glass substrate polished to a 60/40 surface quality and a transmitted wavefront of λ/4 or better. This level of optical precision ensures that the filter will not introduce aberrations or soften the image, preserving the sharpness delivered by your telescope's main optics. The multi-layer, ion-assisted coatings provide durability and resistance to scratching while ensuring wavelength stability regardless of temperature.

    18nm vs. Narrower OIII Filters: The Visual Advantage

    While astrophotographers often use ultra-narrow 3nm or 7nm OIII filters, the 18nm bandpass of this Optolong filter is intentionally wider for visual astronomy. This wider window allows more photons to reach your eye, resulting in a significantly brighter and more comfortable view through the eyepiece.

    • Brighter Image: The 18nm design prevents the image from becoming overly dim, which can happen with narrower filters, especially in telescopes under 8 inches of aperture.
    • Maintains Contrast: It still provides a dramatic contrast boost, making it an ideal middle ground between a broadband UHC filter and a specialized imaging filter.
    • Better for More Objects: The increased brightness makes it effective on a wider range of emission nebulae, not just the very brightest planetary nebulae.

  • What objects work best with the Optolong 18nm OIII filter?

    The Optolong 18nm OIII filter excels on nebulae rich in ionized oxygen. It is most effective on planetary nebulae like the Ring Nebula (M57) and the Dumbbell Nebula (M27), and supernova remnants such as the Veil Nebula complex (NGC 6960/6992). It can also enhance portions of larger emission nebulae like the Lagoon Nebula (M8).

    Will the Optolong 18nm OIII filter make nebulae brighter from my city?

    No, a narrowband filter cannot make an object intrinsically brighter. Its purpose is to increase contrast. It works by blocking over 99% of common light pollution sources, which makes the sky background appear much darker. This allows the faint light from the nebula to stand out more clearly, making it easier to see, but the nebula's actual brightness remains unchanged.

    How will the Optolong 18nm OIII filter improve my view of the Dumbbell Nebula (M27) in my 8" Dobsonian?

    In an 8" Dobsonian, the Optolong 18nm OIII filter will make a dramatic difference on M27, especially from suburban skies. The sky background will darken significantly, causing the nebula's classic "apple core" shape to pop with well-defined edges. You may also begin to see the fainter lobes and internal structures that are often lost in the skyglow without a filter.

    Is the 18nm OIII filter too aggressive for viewing the Orion Nebula (M42) with a 4" refractor?

    For a very bright object like the Orion Nebula (M42), an 18nm OIII filter is an excellent choice. While M42 is bright enough to see without a filter, the OIII filter will isolate the intricate, wispy details in the nebula's core and wings, revealing structure that is normally overwhelmed by the nebula's own brightness. The 18nm bandpass is wide enough that the view in a 4" scope will remain bright and engaging.

    Why choose an 18nm OIII filter instead of a narrower 7nm version for visual observing?

    The 18nm bandpass is specifically optimized for the human eye. Narrower filters, like 7nm or 3nm versions, are designed for CCD/CMOS sensors and can produce an image that is too dim for satisfying visual use, particularly in smaller telescopes. The 18nm filter provides a powerful contrast boost while maintaining enough image brightness for a comfortable and detailed view.

    Can I use the Optolong 18nm OIII filter for astrophotography?

    While it is primarily designed for visual use, you can use the 18nm OIII for astrophotography, especially with one-shot color cameras from light-polluted areas. It provides a stronger signal and more natural star shapes than ultra-narrowband filters. However, for serious narrowband imaging from any location, a dedicated 7nm, 5nm, or 3nm OIII filter will provide higher contrast and better rejection of moonlight.

  • Bandpass 18nm
    Central Wavelength 500nm
    Substrate Material Optical Glass
    Substrate Thickness 1.85mm
    Average Transmission >80%
    Blocking Range 400-700nm
    Blocking Depth >99% of light pollution lines
    Surface Quality 60/40
    Transmitted Wavefront RMS λ/4
    Parallelism 30s
    Available Sizes 1.25" Mounted, 2" Mounted

    • Optolong OIII 18nm Nebula Filter (Selected Size)

      × 1

    • Protective Plastic Case

      × 1

  • Optolong 3-Year Warranty