About the Object:

The Elephant's Trunk is the dark nebula and surrounding, complex emission structure rising prominently from the bottom of the image. It is part of the overall emission nebula IC 1396 which covers the entire image. The Elephant's Trunk itself, IC 1396A, is a swirl of gas and dust whose rim is illuminated by the star HD 206267, the bright triple star near the middle of the frame. That star is extremely hot and bright and is putting out a large amount of ultraviolet light that causes the surrounding gas cloud to fluoresce. The very dark portions of the nebula are areas that are protected from the ultraviolet light by heavy concentrations of dust, so they don't fluoresce. 

The Elephant's Trunk is thought to be a star forming region that is home to several new stars, less than one hundred thousand years old, discovered in infrared images in 2003. Infrared light penetrates dust and gas better than visual light, allowing the young stars to be seen through the dust that surrounds them and absorbs their visual light. IC 1396 is located in the constellation Cepheus at a distance of 2,400 light years. 

About the Image

Most of the data for this image were captured using a dual-band filter and a color camera. The dual-band filter passes Hydrogen alpha light (656nm) as well as doubly ionized Oxygen light (501nm). Using a mathematical blending formula, the different colors contained in the image are mapped to red, green, and blue. This is commonly known as an HOO process since RG&B are represented by Ha, Oiii, & Oiii respectively. In order to get some contrast between the green and the blue, H-alpha light is mixed into the blue channel. By assigning appropriate ratios, the final image is rendered in a palette very similar to the SHO (sulpher, hydrogen, oxygen) palette made famous by the Hubble Space Telescope. While the process is synthetic and the colors are not true to life, the combination does highlight real structures in the nebula. 

In addition to the narrowband data, separate exposures were taken in natural red, green, and blue to capture accurate star colors. The narrowband data were combined with the RGB stars to form the final image. Most of the narrowband data were captured with a nearly full moon visible from a heavily light polluted location. However, narrowband filters allow light pollution to be preferentially suppressed, so even a relatively small telescope can capture faint, low surface brightness objects like the Elephant's Trunk.