Astronomik H-beta 1.25" filter (Astronomik, SKU: 10214125) is a specialist visual filter for nebulae with significant hydrogen H-beta emission at 486 nm. Its narrow passband increases the contrast of these objects while passing only a small portion of other light.
The filter is intended for selected targets such as the Horsehead and California Nebulae. It works best under dark skies, with dark-adapted vision and a suitable magnification. It strongly dims stars and does not replace a general-purpose UHC filter or good observing conditions.
The filter has a 1.25" cell with an M28.5 × 0.6 thread. It fits accessories with a matching filter socket; the nominal cell size is not the diameter of the clear glass aperture.
• selective transmission of the H-beta line
• suited to selected hydrogen nebulae
• best used under dark skies
• durable coatings resistant to scratching and moisture
• filter: Astronomik H-beta 1.25" filter
• protective filter box
• manufacturer: Astronomik
• manufacturer product code: 10214125
• spectral line: H-beta 486 nm
• transmission range: 480–492 nm
• full width at half maximum (FWHM): 12 nm
• typical transmission: 97% at 486 nm
• cell size: 1.25"
• thread: M28.5 × 0.6
• glass thickness: 1 mm
• material: finely polished optical glass
• optical quality: diffraction-limited
• coating resistance: to scratching, moisture and ageing
• parfocality: with standard Astronomik filters using 1 mm glass
H-beta adds the ability to distinguish selected faint hydrogen nebulae more clearly.
