Emission nebula
De Mairan's Nebula (M43)
In Orion (Ori) • Magnitude 9.0 • 20 arcminutes
Open the free AstroPlanner with De Mairan's Nebula pre-selected, scored against your telescope, location, and the live cloud forecast.
A swirling, comma-shaped nebula separated from the Great Orion Nebula (M42) by a dark dust lane, but physically part of the same enormous cloud. Despite appearances, the entire glow of M43 is powered by just a single embedded star — NU Orionis — making it a surprisingly simple structure for something so visually rich.
De Mairan's Nebula at a glance
| Catalog IDs | M43, N 1982 |
| Type | Emission nebula |
| Constellation | Orion (Ori) |
| Right ascension | 05h 35m 35s |
| Declination | -05° 16' 12" |
| Apparent magnitude | 9.00 |
| Surface brightness | 13.5 mag/arcsec² |
| Angular size | 20.0 × 15.0 arcmin |
| Max altitude at 45°N | 40° |
| Best imaging months | Sep, Oct, Nov |
How to image De Mairan's Nebula
De Mairan's Nebula sits in the constellation Orion at right ascension 05h 35m 35s and declination -05° 16' 12". To frame and integrate it well, AstroPlanner will compute the optimal moonless window for tonight from your location, the field-of-view fit against your sensor and focal length, the suggested total integration time given your aperture and sky Bortle class, and a cloud-aware schedule that drops it from the plan if your nearest cloud forecast spike overlaps the best altitude window. As an emission nebula, De Mairan's Nebula responds very well to dual-narrowband filters under city skies.