Astronomik HSO 6nm filter set 2" (M48) H-alpha, SII and OIII

Astronomik's 6nm narrowband emission line filters are ideal for imaging faint objects in star-rich regions of the Milky Way, as they typically halve the number of stars in the image compared to a 12nm filter. They are also suitable if you are using a camera with very low dark current or if you are observing from a location with extreme light pollution.

Astronomik MFR Coating
The Astronomik MFR coating provides the best possible out-of-band blocking across the entire spectral range from UV to IR, extremely high contrast, minimal stray light, no halos, and razor-sharp stars.

12nm MFR-coated filters can be used in all instruments with aperture ratios from f/3 to f/∞ without any significant loss of performance.
6nm MFR-coated filters can be used in all instruments with aperture ratios from f/4 to f/∞ without significant performance degradation.

Technical Specifications

Guaranteed transmission of over 90% (12nm and 6nm) for the H-alpha line (656nm)
Typical transmission of 96% (12nm) and 93% (6nm) for the H-alpha line
Guaranteed transmission of over 90% (12nm and 6nm) for both SII lines (671.7nm and 673.0nm)
Typical transmission of 96% (12nm) and 93% (6nm) for both SII lines
Guaranteed transmission of over 90% (12nm) and 88% (6nm) for the OIII main line (501nm)
Typical transmission of 95% (12nm) and 92% (6nm) for the OIII main line
Glass thickness: 1mm (except Astronomik OWB Type 3 and XT filters)
Fine Polished optical glass, free of streaks, internal stresses, and bubbles
Extremely scratch-resistant and durable coating
Completely resistant to high humidity and aging effects
Astronomik MFR coating (Astronomik Deep-Sky RGB, UV-IR Block L-1, L-2, L-3, and narrowband emission line filters)
Homofocal with other Astronomik filters
Diffraction-limited
Optimized transmission ranges
Supplied in a high-quality, durable filter box

Due to the high-precision machining of the carrier substrate, all Astronomik filters are homofocal with wedge errors that are well below all usual tolerances. Astronomik filters are diffraction-limited, ensuring that the optical performance (resolution and contrast) of your telescope is not compromised. Problems with the focal position and the exact alignment of the images of the individual color channels are effectively eliminated.
All Astronomik filters are ideal for modern cameras, both CMOS and CCD-based models, allowing you to capture the best possible images with your equipment. Sharpness, contrast, and the absence of any reflections or halos are guaranteed. Even with bright stars in the field of view, nebulae and galaxies are imaged with the finest structures.

Every Astronomik filter undergoes rigorous quality control before shipping. In addition, every Astronomik narrowband emission line filter is measured using a high-end PerkinElmer spectrophotometer to ensure it meets the specifications published on our website. On the back of each narrowband emission line filter, you will find a label that provides the precise spectral data for the respective filter, including the maximum transmission and the recommended range of aperture ratios.