Narrowband imaging with OSC CCD camera

Normally a monochrome CCD camera, in combination with color and/or narrowband filters, is used for astronomical imaging. Altough less efficient also a one shot color (OSC) CCD camera can be used for astronomical imaging. A OSC CCD camera is in fact a monochrome camera with a Bayer filter on top. A Bayer filter is a color filter array (CFA) for arranging RGB color filters on a square grid of photosensors. Its particular arrangement of color filters is used in OSC CCD cameras used to create a color image. The filter pattern is 50% green, 25% red and 25% blue, hence is also called RGBG, GRGB, or RGGB.

The raw output of Bayer-filter cameras is referred to as a Bayer pattern image. Since each pixel is filtered to record only one of three colors, the data from each pixel cannot fully determine color on its own.

Most used narrowband filters are H-alpha (656nm, red), OIII (501nm, green) and H-beta (486nm, blue). The data of these three filters can be combined to a narrowband RGB image (like with broadband R,G and B filters). Of course also a synthetic narrowband RGB image can be constructed only using H-alpha and OIII date, see here.

© Copyright Rob Kantelberg
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