Astronomy and Astrophysics – Astronomy
Scientific paper
Nov 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993aj....106.2154b&link_type=abstract
Astronomical Journal (ISSN 0004-6256), vol. 106, no. 5, p. 2154-2160
Astronomy and Astrophysics
Astronomy
12
Image Analysis, Panoramic Scanning, Photographic Emulsions, Photographic Plates, Sky Surveys (Astronomy), Astronomical Photometry, Charge Coupled Devices, Photographic Film, Telescopes
Scientific paper
With the advent of fast scanning microphotometers and inexpensive digital mass storage, there has been a resurgence of interest in performing deep (B less than or equal 25) panoramic surveys by coadding large numbers (approximately 102) of digitized photographic plates. While the Kodak IIIa emulsions are highly linear recorders in photographic grain density, we demonstrate that the threshold and saturation levels which restrict the dynamic range of the emulson can distort the higher statistical moments of the grain density fluctuations (variance, skewness, etc.) along the linear part of the characteristic curve. We illustrate this effect with scanned density step wedges from both IIIa-J and IIIa-F photographic plates. The variance of the grain fluctuations is only additive between digitized plates that preserve the Poissonian grain noise. In order to correct for the statistical distortion, we compute the variance of the fluctuations as a function of density for five scanning aperture sizes (2, 4, 8, 16, and 32 micrometers). The statistical effect, which reduces the linear density regime of a photographic emulsion, is particularly prominent with small scanning apertures and at high photographic density. We suspect that the statistical distortion induced by the limited dynamic range is negligible for scanning apertures larger than approximately equal 12 micrometers which corresponds to approximately equal 0.8 sec at the focal plane of major Schmidt telescopes.
Bland-Hawthorn Jonathan
Malin David F.
Shopbell Patrick Lynn
No associations
LandOfFree
Deep sky surveys: A motivation for stacking digitized photographic plates does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Deep sky surveys: A motivation for stacking digitized photographic plates, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Deep sky surveys: A motivation for stacking digitized photographic plates will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-808011