Sh2-261

Emission nebula Sh2-261 (Sharpless 261, or Lower’s nebula) is a - rarely observed - HII-region located between the galactic Orion and Perseus arm at a distance of about 3200 Lightyears with a diameter of about 13 parsec. The hydrogen gas is ionized by the O7.5V runaway star HD 41997.

Sh2-261 is rather faint, and was discovered in 1939 by Harold Lower.

Emission Nebula Sh2-261, 28 & 30 December 2025, Kempen,

William Optics APO 110 mm, f/7, ASI1600mm pro, gain 139, T = -10C, H-alpha filter [10320 sec], S[II] filter [6120s].

Image processing with PixInsight V.1.9

Sh2-261 is one of the faintest objects which I have imaged with my equipment so far. H-alpha and S[II] data are relatively faint, compared to data from other emission nebulae. Data using the O[III] filter show -with 15 minute exposure - almost no signal, so extended data collection is not very economical. In addition both nights were compromised by the Moon (±65%) and some very thin high clouds and/or fog.