Chroma H-beta 5 nm 65 × 65 mm unmounted filter (Chroma Technology, SKU: CT-27005-65X65) is a narrowband filter for imaging emission nebulae in H-beta. Its selective transmission records the chosen emission component while reducing light outside the passband.
In systems faster than f/4, the filter passband shifts towards shorter wavelengths, which can reduce transmission of the selected line. Selection should account for the actual focal ratio after any reducer or corrector. This version is not optimized for f/3.
The 5 nm passband provides more tolerance for spectral shift than a 3 nm passband, but does not imply full transmission in arbitrarily fast optical systems.
The filter is not intended for observing or imaging the Sun.
• narrow 5 nm passband for recording H-beta emission while suppressing the sky background
• hard interference coatings deposited by magnetron sputtering
• antireflection coatings on the opposite side of the substrate to reduce reflections
• standard design for f/4 and slower systems, meaning higher f-numbers
• parfocal design with Chroma Astronomy filters using the same 3 mm substrate thickness
• filter: Chroma H-beta 5 nm 65 × 65 mm filter, unmounted
• type: H-beta narrowband astrophotography filter
• version: standard, without passband optimization for f/3
• format: unmounted
• glass dimensions: 65 × 65 mm
• bandwidth (FWHM): 5 nm
• passband around the emission line: approximately 486.1 nm
• optical substrate thickness: 3 mm
• transmitted wavefront quality: better than 0.25 waves/inch
• coatings: hard interference and antireflection coatings
• country of manufacture: USA
The filter isolates the selected emission band in an astrophotography setup with a holder matched to its size and format.
