SII 6nm CCD MaxFR - 1.25" (M28.5)
Astronomik
From $199.95
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The Astronomik SII 6nm CCD MaxFR is a narrowband emission-line filter designed specifically for high-quality CCD astrophotography imaging of sulfur-ionized (SII) nebulae and supernova remnants. With a 6nm bandwidth isolating the 671.7nm and 673.0nm SII emission lines, this filter provides guaranteed transmission of over 90% and excels at enhancing contrast in both light-polluted and dark-sky environments. The MaxFR coating enables use across fast optical systems from f/2.2 to f/8, making it ideal for rapid astrographs like RASA and Epsilon telescopes while maintaining diffraction-limited optical performance.
Specifications
| Coating Type | MaxFR |
| Usable Focal Ratio Range | f/2.2 to f/8 |
| Filter Mount Size | 1.25 in |
| Diffraction Limited | ✓ |
| Glass Thickness | 1 mm |
| Filter Type | Narrowband Emission-Line (SII) |
| Thread Type | M28.5 |
| Central Wavelength | 671.7 |
| Bandwidth | 6 |
| Warranty | 10 |
| Blocking Range | UV to IR |
| Typical Transmission | 93% |
| Parfocal | ✓ |