Chroma OIII 3 nm 2" (27006) — ultra-narrowband, M48 threaded ring The Chroma 27006 OIII 3 nm bandpass filter isolates the 500.7 nm primary emission line of doubly ionised oxygen, the next most common nebular emission after H-alpha. Its ultra-narrow 3 nm passband gives maximum contrast and background suppression, ideal under light-polluted skies or bright…
Manufacturer model: Chroma 27006 OIII 3nm, 2-inch M48 threaded ring · Specifications checked against manufacturer data on 2026-11-03
The Chroma 27006 OIII 3 nm bandpass filter isolates the 500.7 nm primary emission line of doubly ionised oxygen, the next most common nebular emission after H-alpha. Its ultra-narrow 3 nm passband gives maximum contrast and background suppression, ideal under light-polluted skies or bright moonlight.
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. Chroma publishes measured spectral data for this filter collimated and at f/2.5 to f/5. For systems around f/3, Chroma offers a separate f/2.8–f/3.6-optimised version.
| Chroma part number | 27006 OIII 3nm Bandpass |
|---|---|
| Target line | OIII, 500.7 nm |
| Bandwidth | 3 nm |
| Format | 2-inch M48 threaded ring |
| 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 27006 OIII 3nm · Chroma f/# performance data
Standard 27006, not the f/2.8–f/3.6 optimised OIII 3nm (27066). Chroma catalogue CWL field reads 500 nm; filter targets 500.7 nm line.
| Target line (nm) | 500.7 |
|---|---|
| Published fnumber data | Collimated, f/2.5, f/3, f/4, f/5 |
Data sheet
Chroma OIII 3 nm 2" (27006) — ultra-narrowband, M48 threaded ring The Chroma 27006 OIII 3 nm bandpass filter isolates the 500.7 nm primary emission line of doubly ionised oxygen, the next most common nebular emission after H-alpha. Its ultra-narrow 3 nm passband gives maximum contrast and background suppression, ideal under light-polluted skies or bright…
Manufacturer model: Chroma 27006 OIII 3nm, 2-inch M48 threaded ring · Specifications checked against manufacturer data on 2026-11-03
