M20 — Trifid Nebula
Emission Nebula in Sagittarius
About
The Trifid Nebula (NGC 6514) in Sagittarius, about 4,100 light-years away. It combines a red emission nebula, a blue reflection nebula and dark lanes (Barnard 85) that split it into three lobes. About 3,100 young stars surround its most massive star.
Imaging tips
- At 870–1,440 mm on APS-C the nebula spans a third to half of the frame; full frame needs about 1,330–2,210 mm.
- Integration reported ranges from 1.2 hours (6-minute subs, DSLR) to 8 hours of 5-minute subs on an unfiltered one-shot colour camera from a dark site.
- One imager's unmodified DSLR did poorly on the hydrogen gas, and another's 1 hour of OIII was too little for the second lobe, so give the weaker signals more time.
- The dark lane Barnard 85 is worth keeping in contrast against the red and blue. M8 (Lagoon) can share a wider frame.
- It sits low: 17° at most from 50°N, so the light crosses a lot of atmosphere; best in June and July.
Facts
- Size
- 28′ × 28′
- Magnitude
- 6.3
- Coordinates
- RA 18h 2.6m, Dec −23° 2′
- Framing, APS-C
- 870–1440 mm
- Framing, full frame
- 1330–2210 mm
- Best months
- Jun, Jul
- Peak altitude
- 17° from 50°N, 32° from 35°N