February: Clusters and Nebulae

Abstract

The Nebulae M78 (bottom) and NGC 2071 (top) are two concentrations of interstellar dust, 1,600 light-years away in Orion. These “reflection” nebulae dimly reflect the blue light of nearby young stars. The other various colors indicate some components of hydrogen and other gases that are excited to higher energy states, which then glow dimly. These nebulae are part of the vast Orion Complex of dust and gas, 1,600 light-years away, which is centered on the Orion Nebula. Imaging. This can be a frustrating object to image. The areas of reflection nebulosity are ill-defined, and fade gradually to darkness. Even stars appear muted, with many obscured by dark dust. A slightly larger field than shown here might frame the objects better. Because the borders are faint and the object is diffuse, binning all channels including luminance is an option, which I chose for this image. Single-shot color and RGB imaging is possible with long exposures, and has the advantage of yielding more natural colors than LRGB methods. Processing. Begin processing with routine techniques. After histogram adjustments with DDP or curves/levels, processing becomes more challenging. These reflection nebulae have low intrinsic contrast, so avoid aggressive sharpening that may generate excessive noise. After correcting color balance, enhance color by either boosting saturation or using match color. If your luminance channel causes the color to pale, apply the luminance with less than 100% opacity, flatten the image, and then enhance color again. You can try applying the luminance a second or third time with greater opacity each time to introduce more detail (Fig. 2.1).