LRGB

LRGB is a method used in astronomical imaging to produce color photographs by combining a high-resolution luminance image with color information captured in the Red, Green, and Blue channels. In this approach, a monochrome camera or a sensor with a clear luminance filter is used to acquire a sharp, detail-rich L image. Separate frames are captured through RGB broadband filters (or with a color camera) to obtain the color channels that encode hue and saturation, though these color frames often have lower resolution and signal-to-noise than the luminance data.

Process overview: L frames are typically taken with longer exposures to maximize detail and signal-to-noise, while R, G, and B frames are acquired with exposures suitable for color accuracy. All frames undergo calibration (darks, flats, biases) and are aligned to a common field. The color channels are processed and scaled, then merged with the luminance data so that the final image retains the color information while preserving the sharpness and detail contributed by the L channel.

Advantages and applications: LRGB can produce high-resolution color images with strong structural detail and improved dynamic range, useful for a wide range of deep-sky objects such as galaxies, nebulae, and star clusters. It is widely used in amateur and some professional astrophotography setups, especially when a monochrome detector is paired with RGB filters.

Limitations: The workflow is more complex than using a single-color channel, requiring careful calibration, alignment, and color balancing to avoid artifacts or color mismatches.