Photometric Theory for Wide-Angle Phenomena
Isophotometry of cometary tails is difficult owing to the large fields of view and high spatial and temporal resolution necessary to describe the phenomena, and because observations are made often at large zenith distances z. This paper addresses the problem of wide-angle photographic photometry with a view to the extraction of a photometric-morphological history of P/Halley (1982i) from the library of images compiled by the Large-Scale Phenomena Network of the International Halley-Watch. An assumption-free moment-sum method is generalized to permit photometric solutions over wide angles. Provided certain conditions are met, standard stars in the field allow a complete solution for extinction, sky brightness, and the characteristic curve. Necessary conditions are that standards be numerous, unsaturated, well-distributed in z and color index, and trailed over angles sufficiently small to minimize photographic effects. A suggestion is made by which this last limitation may be overcome for future comets. Newton's method for the solution of the general nonlinear least-square problem is formulated, and implemented for a canonical data set. A special inherently linear case is solved analytically to confirm the numerical solutions. The problem of random and systematic photometric errors in the standards is analyzed and discussed, and effects on the extinction and photometric coefficients are deduced.
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| Work Title | Photometric Theory for Wide-Angle Phenomena |
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| License | CC BY-NC-SA 4.0 (Attribution-NonCommercial-ShareAlike) |
| Work Type | Article |
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| Publication Date | July 1990 |
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| Deposited | March 22, 2025 |