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Proceedings Paper

The Mode Filter: A Nonlinear Image Processing Operator
Author(s): Donald C. Wells
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Paper Abstract

The estimation of the low spatial frequency background signals in astronomical digital imagery is a fundamental problem of all the photometric techniques used with such imagery. This problem is particularly acute when numerous foreground sources (stars, galaxies, etc.) are present, because the statistical distribution of background pixel values is skewed. All linear lowpass filters (e.g., the running mean) produce biased estimates in this situation, and the result is biased photometry of the foreground sources, which can produce subtle errors in luminosity functions and other results derived from the photometry (e.g., the apparent number of faint sources may be inversely related to the number of bright sources). These problems can be mostly avoided in many situations by estimating the mode of the skewed distribution rather than the mean. This paper describes a lowpass-filter program which computes an estimate of the mode of the image values in a region around each pixel of an image.

Paper Details

Date Published: 3 May 1979
PDF: 4 pages
Proc. SPIE 0172, Instrumentation in Astronomy III, (3 May 1979); doi: 10.1117/12.957111
Show Author Affiliations
Donald C. Wells, Kitt Peak National Observatory (United States)

Published in SPIE Proceedings Vol. 0172:
Instrumentation in Astronomy III
David L. Crawford, Editor(s)

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