Description (Wikipedia, auto translated from Italian)

Sh2-261, also sometimes known as the Lower Nebula, is an emission nebula visible in the constellation Orion.

It is located in the northernmost part of the constellation, about 6° west of Alhena (γ Geminorum); it is easily visible in long-exposure photos taken even with medium-power amateur tools. It lies in the bright wake of the Milky Way in opposition to the galactic center and is surrounded by rich background star fields. The best period for its observation in the evening sky falls in the months between January and May, and although it is located in the northern celestial hemisphere, it can be observed from all populated areas of the Earth.

It is an H II region located on the outer edge of the Orion Arm, at the limit of the galactic region between this and the Perseus Arm; it is located on the line of sight of the southernmost part of the Gemini OB1 association. One of the stars responsible for the ionization of the gases in the region would be the blue star HD 41997, a fugitive star of spectral class O7.5V;[3] to this are added other stars, including the blue star BD+15°1079, of class B0. This star has sometimes been referred to as class O7, thus moving the distance of the nebula up to 2000 parsecs due to the increase in the discrepancy between absolute magnitude, evidently brighter in a class O star, and apparent magnitude; through the analysis of the other ionizing stars, a distance of approximately 1000 parsecs (3260 light years) was calculated, which seems to be more reliable, also given the redetermination of the star BD+15°1079 as belonging to the B0 class.

Personal Note
After shooting some obscure, small objects (gravitational lense, planetary nebula) I now have a nice, fat emission nebula in bright false colors. I processed as SHO and using foraxx approach and in the end the former came out as most pleasing. I wanted make the blue color pop and bring out the details in the bottom ridge of the nebula. In the end I used the NarrowbandNormalization script to move the dominant color from yellow towards more red.

Processing
SHO: WBPP with 2x drizzle, GradientCorrection, SHO combination, Autolinearfit, Deconvolution, Noice reduction, Star removal, GHS, NarrowbandNormalization, RangeMask, Curves
Lum: using Ha image; UnsharpMask, MMT
RGB: WBPP, GradientRemoval, GHS, curves, rescreen