Player One 1.25" SII 7nm Narrowband Filter

Overview. The Player One 1.25" SII 7nm Narrowband Filter is an S-series singly-ionized sulfur (SII) emission-line filter for monochrome deep-sky astrophotography. It transmits a narrow 7nm ±0.5nm band on the SII emission of nebulae while rejecting the rest of the spectrum, recording the sulfur channel used in Hubble-palette imaging with high contrast even under moderate light pollution. The filter uses a high-quality optical glass substrate with a multi-layer composite coating and threads into standard 1.25" filter mounts.

Who It's For. This filter suits imagers using monochrome cameras who want to capture the SII channel of emission nebulae and complete a tricolor (SHO) narrowband dataset, or continue imaging on moonlit and light-polluted nights.

Key Features & Design.

• Narrow 7nm passband: a 7nm ±0.5nm FWHM isolates the SII emission and rejects most skyglow and broadband light pollution.
• Deep blocking: OD3 blocking (less than 0.1% off-band transmission) with NIR cutoff across 700–1100nm suppresses stray light.
• High in-band throughput: approximately 90% peak transmittance preserves faint sulfur signal.
• Multi-layer composite coating: on a high-quality optical glass substrate for consistent response.
• Standard 1.25" format: M28.5×0.6 cell fits common 1.25" filter wheels and drawers.

Optical/Mechanical Design. The filter passes a 7nm ±0.5nm FWHM band on the SII emission line and holds OD3 off-band blocking (<0.1% transmission) with the near-infrared blocked from 700–1100nm. Peak in-band transmittance is about 90%. Both surfaces are polished to 1/4 lambda surface accuracy on a 2.0 ±0.03 mm optical glass substrate carrying a multi-layer composite coating. The anodized cell uses M28.5×0.6 (1.25") threads and measures 7.5mm overall (5mm body plus 2.5mm thread).

Recommended Uses. Narrowband imaging of emission nebulae, HII regions, and supernova remnants; the SII channel in tricolor (SHO) Hubble-palette processing; and deep-sky capture during bright-moon or light-polluted conditions.

Compatibility & Accessory Notes. The M28.5×0.6 cell fits standard 1.25" filter wheels, drawers, and 1.25" nosepieces. It pairs with matching Player One 1.25" Ha 7nm and OIII 7nm filters for a complete SHO set. Narrowband filters are intended for monochrome imaging cameras; on one-shot-color sensors the effective throughput is reduced.

Good to Know Before You Order.

• Individual center wavelength: Player One does not publish a numeric center wavelength for this line on the product page, so it is not stated here.
• Shipping weight: a packaged weight is not published by the manufacturer; contact us if you need it before ordering.
• Camera type: narrowband results are strongest with monochrome cameras.

FAQ.

Is it difficult to set up? No. The filter threads into any standard 1.25" filter wheel, drawer, or nosepiece and needs no adjustment once installed.

Will it help under light pollution? Yes. The 7nm passband rejects most broadband skyglow, so SII emission is recorded with strong contrast even from suburban skies.

Can I use it with a color camera? It is designed for monochrome cameras; a one-shot-color sensor will pass the band but with reduced efficiency.

Bottom Line. A well-coated 7nm SII filter in the convenient 1.25" format, the Player One 1.25" SII 7nm records high-contrast sulfur-line detail and completes the SHO narrowband set.