A graphics data file format established as a standard for graphics file compression and storage. An internally illuminated container which uses indirectly placed light sources to evenly illuminate a translucent diffuser screen on one side of the container. The screen is sized to cover at least the entire aperture of a telescope so that accurate flat-field frames can be made. Synonymous with brightness. The degree of randomness or unpredictability in a signal.
Noise components are a primary determinant of the quality of an image.
Short for picture element. Each cell which constitutes an intersection of the grid of rows and columns on a CCD array is a pixel. After image processing, a measurement of the processed brightness of a pixel. The visible and measurable smear of photons from a point source. Optical diffraction and atmospheric distortion are primary factors causing light from point sources such as distant stars to be smeared into a PSF much larger than the geometrically calculable size of the point source.