Sh2-223 is a faint emission nebula (H II region) located in a dense starfield in the constellation Auriga. It is a huge H II region, a large cloud of partially ionized gas where star formation can occur. It appears as a large, faint red arc or “wing” in deep-sky images. Its red glow comes from ionized hydrogen-alpha (Hα) emissions. The nebula is believed to be ionized by the star BD +41 1144 (an O7.5 V star) or possibly LS V +40 46.
In addition to the predominant Hii, there is also a significant amount of Oiii in the area. This leads to a bluish tinge or a slight purplish hue in parts of the image.
It is considered a difficult target for astrophotographers because of its extreme faintness. It often requires long total integration times, such as 25+ hours, to resolve clearly. Separating the IFN from the Hii nebula requires data. This photograph is only 11.4 hours. More to come in the future if the opportunity presents itself.
Image acquisition using Astro Photography Tool (APT). Subframe calibration, alignment, integration, and processing using PixInsight. Astrobin link for acquisition details and an annotated image.
