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Paper: A Technique for Stacking Digitized Photographic Plates
Volume: 52, Astronomical Data Analysis Software and Systems II
Page: 398
Authors: Bland-Hawthorn, Jonathan; Shopbell, Patrick L.
Abstract: With the advent of fast scanning microphotometers and inexpensive digital mass storage, there has been a resurgence of interest in performing deep (B <= 25) panoramic surveys by co-adding large numbers ( ~ 10(2) ) of digitized photographic plates. While the Kodak IIIa emulsions are highly linear recorders of photographic grain density, we demonstrate that the threshold and saturation levels which restrict the dynamic range of the emulsion can distort the higher statistical moments of the grain density fluctuations (variance, skewness, etc.) along the linear part of the characteristic curve. The variance of the grain fluctuations is only additive between digitized plates that preserve the Poissonian grain noise. In order to compensate for the statistical distortion, we derive the necessary pixel weighting for five scanning aperture sizes (2mu m, 4mu m, 8mu m, 16mu m, 32mu m) as a function of the grain density.
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