iOptron SII Narrowband Filter -1.25"
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The iOptron SII narrowband filter is designed specifically for astrophotography of emission nebulae, isolating light at approximately 672 nm (the Sulfur II emission line) while suppressing many unwanted wavelengths such as skyglow and common artificial‑light emissions.
Key Features:
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Mounted in a standard 1.25″ (M28.5 × 0.6) cell, making it compatible with 1.25″ filter wheels and eyepieces.
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Multi‑layer anti‑reflection coating for high light‑transmission and minimal loss.
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High optical quality: surface‑flatness better than λ/4, surface quality rated 60/40, parallelism ~30″.
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Engineered to reduce background light from artificial sources (mercury vapor, sodium vapor, skyglow) to boost the contrast of nebula structures.
Why it stands out:
This SII filter is an effective tool for deep‑sky imagers who wish to capture the red‑orange Sulfur emission line and include it as part of a multi‑filter (e.g., SHO or Hubble‑palette) workflow. By selectively passing just the 672 nm band, it helps separate the Sulfur component from other emission lines and ambient light, yielding clearer, higher‑contrast nebula images.
Typical Use Cases:
- Used with monochrome astrophotography cameras and a filter wheel when capturing faint emission nebulae.
- Ideal for combining with H‑alpha and OIII narrowband filters to create tri‑color narrowband imagery (Sulfur‑Hydrogen‑Oxygen palette).
- Useful for enhancing the visibility of faint structural features in nebulae by suppressing unwanted broadband skyglow.
- Fit into an imaging train where you have a 1.25″ filter slot ahead of your camera for lens/telescope systems.
- “Isolate the Sulfur emission line at 672 nm for vivid nebula detail.”
- “Premium narrowband 1.25″ mounted filter for high‑contrast astrophotography.”
- “Optimised for deep‑sky imaging of emission nebulae, suppressing skyglow and artificial light.”