Optolong SII Filter 6.5nm 1.25" (31.8mm)
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Vai al moduloOptolong SII Filter 6.5nm 1.25" (31.8mm) for Narrowband Astrophotography
The Optolong SII 6.5nm 1.25" is a narrowband Sulfur II (672 nm) filter designed for deep-sky astrophotography with CCD and CMOS monochrome cameras. With a 6.5 nm bandwidth centered at 672 nm, it selectively isolates the SII emission line, significantly improving contrast on emission nebulae even under light-polluted or moonlit skies.
Optimized for SHO Imaging (H-alpha, OIII, SII)
This SII filter is engineered for use in combination with H-alpha and OIII filters in a SHO narrowband setup, enabling tricolor imaging in the well-known Hubble palette style. Narrowband imaging with an SHO set can be performed even in urban environments, as the filter enhances the contrast between nebula and background sky.
A narrowband filter does not increase object brightness but improves signal isolation by suppressing unwanted wavelengths, especially artificial light pollution lines such as sodium (589 nm) and mercury (435 nm, 578 nm), as well as atmospheric skyglow.
Optical Performance and Transmission Control
The filter delivers 80% transmission at the SII 672 nm line and provides off-band suppression down to 0.1% (OD3). It also blocks infrared wavelengths from 700–1100 nm, ensuring controlled spectral response and improved imaging precision.
Not suitable for solar observation or imaging.
Precision Construction and Filter Cell
Manufactured using Schott optical glass with a 2.0 mm substrate thickness, the filter meets strict optical tolerances for flatness and parallelism. The ultra-slim filter cell minimizes vignetting and maximizes clear aperture (26 mm for 1.25"). The Aerometal CNC-machined housing features black anodized finishing and internal anti-reflection treatment to reduce stray light.
Technical Specifications
| Filter Type | SII Narrowband |
| Central Wavelength | 672 nm |
| Bandwidth | 6.5 nm |
| Transmission at SII | 80% |
| Off-Band Transmission | 0.1% (OD3) |
| IR Blocking | 700–1100 nm |
| Substrate Material | Schott optical glass |
| Thickness | 2.0 mm |
| Surface Quality | 60/40 (MIL-O-13830) |
| Flatness | 1/4 λ |
| Parallelism | < 30″ |
| Format | 1.25" (31.8 mm) |
| Clear Aperture | 26 mm |
The Optolong SII 6.5nm 1.25" is a precision-engineered solution for narrowband deep-sky imaging, ideal for emission nebula photography and advanced SHO astrophotography workflows.