NGC 6188 Close-up

NGC 6188, also known as RCW 108, is an active star-forming region in the constellation Ara and part of the Ara OB1 stellar association. The nebula is ionized and eroded by the UV radiation emitted by the O-type stars in the open cluster NGC 6193. Prominent bright rims mark the ionization fronts and clearly indicate that the radiation originates from the direction of the cluster. The region also contains numerous dark clouds as well as reflection nebulae, which point to ongoing star formation, some of it hidden at optical wavelengths.

NGC 6188 is a popular target for astrophotographers in the southern hemisphere. I have imaged this nebula several times using different setups. Most images of this object are taken with narrowband filters and processed in various color palettes, such as the Hubble palette. The delicate dark-cloud structures silhouetted against the glowing gas invite imaginative interpretation; many observers see a dragon shape, which has earned the nebula the nickname “Fighting Dragons of Ara.”

For this image, I deliberately aimed for a natural color rendition and therefore used an LRGB filter approach. In addition, I acquired data with a very narrow Hα filter. Integrating the Hα signal into the final LRGB image was not trivial. It was important to me to preserve the nebula’s blue-turquoise appearance, which is caused by OIII emission and reflection of the light from the hot O-type stars. For that reason, the Hα contribution was blended in very subtly. Below the final image, I also provide the pure Hα frame for comparison.