C11 — Bubble Nebula
Emission Nebula in Cassiopeia
About
An emission nebula in Cassiopeia, about 7,100 light-years away. The wind from the massive young star SAO 20575 blows a shell of gas around itself, and the nearby cloud glows in response. William Herschel found it in 1787. Caldwell 11.
Imaging tips
- Plain RGB hides much of this nebula, so shoot narrowband: one imager isolated it with a 6 nm Ha filter, and a mono camera produced an HOO version.
- The shell is only 15′ × 8′, so 1620–2690 mm on APS-C spans a third to half of the frame; one write-up used a 1050 mm refractor.
- M52 lies about 35′ away, so a wide lens or short scope can put both in one frame, and the Lobster Claw Nebula can join with the right magnification.
- One imager's best result came from about 6 hours of exposure, shot from a light-polluted backyard.
- Best in August and September; it peaks near 79° altitude from 50°N.
Facts
- Size
- 15′ × 8′
- Magnitude
- 10.0
- Coordinates
- RA 23h 20.8m, Dec +61° 12′
- Framing, APS-C
- 1620–2690 mm
- Framing, full frame
- 2480–4130 mm
- Best months
- Aug, Sep
- Peak altitude
- 79° from 50°N, 64° from 35°N