Sh2-261, also known as Lower’s Nebula, is a faint and expansive emission nebula located in the constellation Orion, approximately 3,000 light-years from Earth. This large H II region is energized by embedded massive stars whose ultraviolet radiation ionizes the surrounding hydrogen gas, producing the characteristic deep red H-alpha glow. Unlike more compact nebulae, Sh2-261 spans a wide area of the sky with subtle variations in brightness, making its full structure difficult to capture.
The interaction between stellar radiation and the surrounding interstellar medium creates a complex network of diffuse emission, dark dust lanes, and softly defined boundaries. Wispy filaments and broad, cloud-like regions blend together, giving the nebula a layered and almost translucent appearance. Its low surface brightness and lack of sharply defined features present a significant imaging challenge, requiring long integration times and careful processing to reveal its faint, extended structure.
This image was created using a combination of narrowband H-alpha, SII, and OIII data along with broadband RGB stars acquired from Arnold, CA. The data were collected between December 8, 2025 and February 10, 2026, with a total integration time of 38.6 hours.