Astronomik H-alpha 12 nm XT Clip-Filter Nikon Z XL (Astronomik, SKU: 10215090) is a narrowband filter for imaging nebulae emitting light from hydrogen H-alpha at 656 nm. Its 12 nm full width at half maximum increases the contribution of the selected emission relative to the sky background, both at dark sites and under light pollution.
The filter suppresses light outside the useful passband, from UV to IR. It can be used for monochrome imaging or to build composites from exposures taken through several emission-line filters. Exposure time and channel balance depend on the brightness of the individual lines, camera sensitivity and sky conditions.
The 12 nm passband preserves more starlight than narrower versions, which can help when guiding uses light passing through the filter. It is a useful entry into narrowband imaging; a narrower passband does not always help when the exposure background is mainly limited by camera noise.
The XT version uses a very thin substrate to reduce additional aberrations at the frame edges with wide-angle lenses. Parfocality with standard filters using 1 mm glass should not be assumed; check focus after changing the filter.
The Clip mount places the filter inside a compatible camera body, in front of the sensor. This allows the same filter to be used with different compatible lenses or a telescope and reduces dust settling on the sensor. The correct version must be selected for both the camera model and the lens.
The H-alpha filter is not a solar filter and must not be used for observing or imaging the Sun.
• passband: H-alpha, 12 nm full width at half maximum
• suppression of unwanted out-of-band light from UV to IR
• recording of one emission-line channel for later combination
• coating: Astronomik MFR
• mounting inside a compatible camera, in front of the sensor
• durable coatings resistant to scratching and moisture
• thin XT substrate for use with wide-angle lenses
• filter: Astronomik H-alpha 12 nm XT Clip-Filter Nikon Z XL
• protective filter box
• manufacturer: Astronomik
• manufacturer product code: 10215090
• type: H-alpha narrowband emission-line filter
• full width at half maximum (FWHM): 12 nm
• guaranteed transmission: over 90% at the H-alpha line at 656 nm
• typical transmission: 96% at the H-alpha line at 656 nm
• out-of-band blocking: from UV to IR
• coating: Astronomik MFR
• recommended focal ratio range: f/3–f/∞
• mount: Clip-Filter Nikon Z XL
• compatible bodies: Nikon Z5, Z6, Z6II, Z6III, Z7, Z7II, Z8, Z9, Zf
• incompatible: Nikon APS-C cameras and Nikon Z TC-2.0x teleconverter
• substrate: very thin, XT version
• material: finely polished optical glass
• optical quality: diffraction-limited
• coating resistance: to scratching, moisture and ageing
• quality control: individual measurement of spectral response
Selective H-alpha imaging helps reveal nebular structure with a reduced sky-background contribution.
