iOptron H-Alpha Narrowband Filter -1.25"
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The iOptron H‑Alpha Narrowband Filter is a high‑performance astrophotography accessory, specially built for deep‑sky imaging of emission nebulae. This filter is mounted in a 1.25″ (approximately 31 mm) threaded cell, making it compatible with most 1.25″ filter wheels and visual eyepiece holders.
Key Features:
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Passes a narrow bandwidth centered at ~656 nm (Hydrogen‑alpha emission line) with about 7 nm full width at half maximum (FWHM).
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Multi‑layer anti‑reflection coating to ensure high transmission of the target wavelength and minimal loss.
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Mounted in a precision‑threaded 1.25″ (M28.5×0.6) cell, compatible with standard 1.25″ filter wheels (such as the iOptron iEFW series) and 1.25″ eyepiece connections.
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Optical build quality: surface flatness better than λ/4, parallelism around 30″, surface quality rated 60/40.
Why it stands out:
This H‑Alpha filter is a smart choice for astrophotographers who want to isolate the rich red emission of hydrogen present in many emission nebulae (such as the North America Nebula, Pelican Nebula, or the Rosette Nebula). By allowing only the narrow H‑alpha line to pass—and rejecting much of the unwanted light from artificial sources (mercury and sodium vapour lamps) and “skyglow” background—this filter enhances the contrast between nebula and night sky.
Typical Use Cases:
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With a monochrome astrophotography camera and a filter wheel: use the H‑Alpha filter to capture the red emission channel, then combine with other filters (e.g., RGB or narrowband) for full‑colour or enhanced‑detail imaging.
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Ideal for deep‑sky imaging where light pollution is present—narrowband filters help suppress background sky brightness, making faint nebula structure more visible.
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Compatible with your existing 1.25″ imaging train: simply mount this filter in your filter wheel or directly in the optical path for visual use on nebulae.