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IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.
Explore Scientific Nebula Filter S-II 1.25-inch 6.5nm
Explore Scientific Nebula Filter S-II 1.25-inch 6.5nm
Explore Scientific Nebula Filter S-II 1.25-inch 6.5nm
Explore Scientific Nebula Filter S-II 1.25-inch 6.5nm

Explore Scientific Nebula Filter S-II 1.25-inch 6.5nm

by Explore Scientific
SKU ES-310125
$199.99 - $199.99
$199.99
$199.99 - $199.99
$199.99
Price Match Policy!
  • Isolates the ionized sulfur (S-II) emission line at 672nm
  • Ultra-narrow 6.5nm bandpass for maximum contrast
  • Standard 1.25-inch barrel size fits most eyepieces and accessories
  • Blocks light pollution and other interfering wavelengths
  • Includes an individual test report for quality assurance
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Downloads
  • Warranty

  • Explore Scientific Nebula Filter S-II 1.25-inch 6.5nm

    The Explore Scientific S-II Nebula Filter isolates the specific 672nm emission line from ionized sulfur using an exceptionally narrow 6.5nm bandpass. Designed for the standard 1.25-inch format, this filter dramatically increases contrast on specific deep-sky objects by rejecting virtually all other sources of light, especially artificial light pollution.

    Isolating Ionized Sulfur: The 6.5nm Bandpass at 672nm

    This filter is engineered to transmit light only within a 6.5nm window centered on the 672nm wavelength characteristic of ionized sulfur. This extreme selectivity is the key to defeating light pollution; by blocking streetlights and skyglow, the filter reveals the faint signal of the nebula against a much darker background. Each Explore Scientific filter includes an individual test report, verifying that its bandpass meets the precise specification required for this high-contrast observation.

    The primary trade-off of such a narrow filter is that it significantly dims stars, which can make locating your target via star-hopping more challenging. However, for revealing the hidden structure within emission nebulae, the benefit is transformative.

    6.5nm Contrast Boost: Revealing Faint Emission Nebulae

    Under a light-polluted sky, many nebulae are completely invisible. With the 6.5nm S-II filter, structures suddenly appear in areas of the sky that seemed empty moments before. It excels at making planetary nebulae, complex emission nebulae, and supernova remnants observable from urban and suburban locations.

    This filter is a critical tool for both visual observers seeking to push their equipment to its limits and for astrophotographers. For imagers, the S-II signal provides crucial data for creating detailed, multi-wavelength color composites that reveal the chemical composition of a nebula.

    S-II vs. H-alpha: Mapping Nebulae in Different Wavelengths

    While an H-alpha filter captures the dominant hydrogen signal in most emission nebulae, an S-II filter reveals different structures and details. In astrophotography, these two filters are often used with an O-III filter to create the "Hubble Palette" (SHO), where each element is assigned to a different color channel.

    • Hydrogen-alpha (H-alpha): Typically the strongest signal, revealing the primary shape and brightest areas of a nebula.
    • Sulfur-II (S-II): Often traces regions of different temperatures and ionization, frequently highlighting the outer, wispy edges of a nebula or shock fronts that are less prominent in H-alpha. Adding S-II data provides depth and structural context that H-alpha alone cannot capture.

  • What is the main purpose of the Explore Scientific 6.5nm S-II filter?

    Its primary purpose is to dramatically increase the contrast of emission nebulae by isolating the light they emit from ionized sulfur (S-II) at a wavelength of 672nm. The narrow 6.5nm bandpass blocks out light pollution, allowing you to see or photograph faint nebular details that would otherwise be lost in skyglow.

    Can I use the 1.25-inch S-II filter for visual observing?

    Yes, absolutely. While narrowband filters like S-II are essential for astrophotography, they are also powerful tools for visual observers, especially with larger aperture telescopes (typically 8 inches or more). They can make faint supernova remnants like the Veil Nebula (NGC 6960) or details in the Lagoon Nebula (M8) pop against a dark sky background.

    How would this S-II filter perform on the Eagle Nebula (M16) from a suburban location?

    The Eagle Nebula (M16) is rich in both hydrogen and sulfur. From a suburban location, this 6.5nm S-II filter would be highly effective at isolating the nebula's light from city skyglow. While an H-alpha filter would show the brightest structures, the S-II filter would highlight different areas within the "Pillars of Creation" and surrounding nebulosity, revealing structural details that are often mapped as red or orange in Hubble Palette images.

    I already have an H-alpha filter. Why do I need this Explore Scientific S-II filter?

    An S-II filter is the logical next step after H-alpha for any serious imager. While H-alpha captures a nebula's main structure, S-II captures a different set of physical conditions. Combining S-II data with H-alpha (and O-III) allows you to create full-color narrowband images (like the Hubble Palette) that reveal far more scientific and aesthetic detail than a monochrome H-alpha image alone.

    Will this 1.25" S-II filter work with my DSLR camera?

    A stock, unmodified DSLR camera has a built-in filter that blocks most of the deep red light at the 672nm S-II wavelength. To use this filter effectively for astrophotography, you need a camera that has been "astro-modified" to have increased red sensitivity, or a dedicated astronomy camera which is already sensitive to this wavelength.

    What does the included individual test report for the S-II filter guarantee?

    The individual test report is your assurance of quality. It provides a chart showing the actual transmission curve for your specific filter, verifying that it meets the advertised 6.5nm bandpass and is correctly centered on the 672nm S-II wavelength. This guarantees you are getting a high-performance filter without manufacturing defects.

  • Explore Scientific Warranty