October: Halloween Treats

Abstract

The Cocoon Nebula is a stellar nursery, with its delicate fabric of glowing hydrogen torn asunder by the solar wind of newborn stars. Imagine scanning the heavens from a planet within this nebula. While we envision a glowing scarlet sky obscuring most stars, in reality the inhabitants would barely notice the nebula. The faint rustic shade emitted by the hydrogen cloud would just contribute to the background canvas of the night sky. Beyond the central glow of hydrogen, the surrounding interstellar dust begins to dominate. At the edge of the red emission nebula, this dust reflects pale blue light. Farther away, the dust fades, and instead blocks the light of background stars. Imaging. You have many options for framing the Cocoon Nebula. A small field of view, as in my image, provides the most detail in the nebula. A larger field of view, of about 30 arcmin, shows a greater extent of the surrounding dark nebula. An even larger field of 70 arcmin reveals the dark nebula Barnard 168 extending to the west of the Cocoon Nebula. The Cocoon Nebula is relatively bright, and can be imaged with either LRGB, RGB, or single-shot color methods. An H-alpha luminance enhances the red nebulosity but is not necessary. Processing. Begin by routinely calibrating, aligning, and combining your images. If your images are high resolution with long exposures, consider deconvolution of a luminance or synthetic luminance channel. Adjust your histogram with either digital development or curves/levels. If applying a red or H-alpha luminance layer, use well under 100% opacity to avoid suppression of the faint blue reflection at the outer border of the red emission nebulosity. Sharpen the brighter areas of the nebula, and smooth the dimmer areas that appear noisy (Fig. 10.1).