Chroma H-alpha 3 nm 36 mm (27001) — ultra-narrowband, unmounted The Chroma 27001 H-alpha 3 nm bandpass filter isolates the 656.3 nm hydrogen-alpha line, essential for imaging nebulae rich in ionised hydrogen. Its ultra-narrow passband separates H-alpha from the nearby SII doublet and gives maximum contrast and background suppression, even under light…
Manufacturer model: Chroma 27001 H-alpha 3nm, 36 mm unmounted · Specifications checked against manufacturer data on 2026-11-03
The Chroma 27001 H-alpha 3 nm bandpass filter isolates the 656.3 nm hydrogen-alpha line, essential for imaging nebulae rich in ionised hydrogen. Its ultra-narrow passband separates H-alpha from the nearby SII doublet and gives maximum contrast and background suppression, even under light pollution or bright moonlight. This 36 mm unmounted version suits filter wheels for APS-C and similar sensors.
Made on a single high-grade glass substrate with hard sputtered coatings and no lamination, the filter withstands humidity and temperature extremes. The primary coating is on the front and an AR coating on the back to prevent ghosts. For systems around f/3, Chroma offers a separate f/2.8–f/3.6-optimised version (27065).
| Chroma part number | 27001 H-alpha 3nm Bandpass |
|---|---|
| Target line | H-alpha, 656.3 nm |
| Bandwidth | 3 nm |
| Format | 36 mm diameter, unmounted |
| Coating | Hard sputtered; AR-coated back face |
| Substrate | Single glass substrate; 3 mm thick (Chroma astronomy brochure) |
| Recommended focal ratio | f/4 and slower for this standard version |
Chroma H-alpha filters · Chroma f/# performance data
Standard 27001, 36 mm unmounted; needs 36 mm unmounted filter wheel/holder. Not 27065 (f/3 optimised).
| Target line (nm) | 656.3 |
|---|
Data sheet
Chroma H-alpha 3 nm 36 mm (27001) — ultra-narrowband, unmounted The Chroma 27001 H-alpha 3 nm bandpass filter isolates the 656.3 nm hydrogen-alpha line, essential for imaging nebulae rich in ionised hydrogen. Its ultra-narrow passband separates H-alpha from the nearby SII doublet and gives maximum contrast and background suppression, even under light…
Manufacturer model: Chroma 27001 H-alpha 3nm, 36 mm unmounted · Specifications checked against manufacturer data on 2026-11-03
