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Sh2-261, widely known as Lower’s Nebula, is a faint and expansive emission nebula situated approximately 3,300 light-years away in the constellation Orion. Tucked away in the northernmost reaches of the Hunter, near the border of Gemini, this ionized hydrogen cloud offers a more subtle and sophisticated target than its famous neighbor, the Great Orion Nebula.

The nebula glows with a characteristic deep red hue, fueled by the intense ultraviolet radiation from the massive, hot blue star HD 41997. This O-type star acts as the primary engine for the region, exciting the surrounding hydrogen gas and causing it to fluoresce. Unlike many dense, compact nebulae, Sh2-261 is characterized by its delicate, wispy structures and a central “void” or darker region that gives it a distinctive, eye-like appearance—earning it the nickname the “Eye of Ra.”

Beyond its visual appeal, Sh2-261 serves as a fascinating laboratory for studying the interaction between massive stars and the interstellar medium. The nebula is a classic H II region, where the radiation pressure from central stars carves out bubbles and shapes the surrounding gas into intricate filaments. These structures are often punctuated by dark dust lanes that provide a sharp contrast against the glowing background, highlighting the turbulent environment of this stellar nursery.

For astrophotographers, Sh2-261 is a rewarding but challenging subject that demands significant integration time. Because it is relatively dim and dominated by hydrogen emission, it is an ideal candidate for narrowband imaging, particularly through an H-alpha filter, which helps to pull out the faint outer shells and internal textures that are often lost in broad-spectrum RGB shots. Its large apparent size—roughly the diameter of the full moon—makes it a perfect fit for wide-field setups looking to capture the “hidden” side of Orion.

Imaging Notes

All of these blending examples are found in the Channel Integration tutorial.

Imaging Workflow

This image followed the Narrowband workflow