Northern Michigan University1, Physics, Marquette, MI 49855 Northern Michigan Unversity2, Physics, Marquette, MI 49855
Astronomers want images that accurately represent light levels in the night sky. CCD cameras can do this, but the images are affected by telescope optics and the camera’s electronics. Additionally, an image can be affected by tracking and atmospheric conditions. Optical vignetting, thermal noise in the camera, and digitization effects can be corrected with established techniques, using additional images of a uniform target (flat fielding), a no-light exposure (dark frame), and a no-time exposure (bias frame). If tracking and atmospherics are poor, then a process called track-and-stack can be used, where many short exposures are combined to create the effect of one long exposure. The resulting image can then be corrected using the above techniques. We discuss the application of these standard techniques to sample images from a laboratory and images taken of the night sky.
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