Sh2-261 — Lower's Nebula
HII Region in Orion
About
Lower's Nebula, a faint hydrogen cloud in northern Orion, near the Gemini border. Harold Lower and his son Charles, amateurs from San Diego, recorded it on a plate in 1939. Its distance is uncertain: one radio measurement gives about 6,200 light-years, and other estimates differ widely.
Imaging tips
- Stewart Sharpless gave its diameter as 45′ in 1959 and described the outline as irregular.
- Very faint to the eye: one source calls it barely visible as a faint haze in a 16–18 inch telescope, so it is a camera target.
- Emission nebula, so use Hα or narrowband. One imager took 24 hours of SHO data; another used 8 hours 45 minutes of Hα plus RGB.
- The brightest part surrounds HD 41997, an O-type star, which sits near the centre.
- Best in December and January; it peaks near 56° altitude from 50°N.
Facts
- Size
- 40′
- Magnitude
- —
- Coordinates
- RA 6h 9.0m, Dec +15° 48′
- Framing, APS-C
- 610–1010 mm
- Framing, full frame
- 930–1550 mm
- Best months
- Jan, Dec
- Peak altitude
- 56° from 50°N, 71° from 35°N