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Session 2 - Applied History of Astronomy II.
Oral session, Sunday, January 14
Salon del Rey Central, Hilton

[2.04] Solar Diameter Measurements from Historical and Recent Solar Eclipses

D. Dunham, A. Fiala, S. Sofia (JHU-APL, USNO, Yale)

During the past 20 years, timings of eclipse 2nd and 3rd contacts, and other Baily's bead phenomena, have been made near the edges of the paths of totality and annularity of several solar eclipses. Different techniques have been used, including visual, photographic, and video observations of the direct or projected solar image formed with telescopes. Historical observations of sufficient accuracy made near total eclipse limits have been found in the literature going back to 1715; most of these are direct visual observations. Analysis of these observations have revealed probable small variations of the solar diameter. Results from the past century can be compared with global weather observations to help resolve the question of whether global temperature changes are caused more by natural solar variations or by anthropomorphic causes such as increased burning of fossil fuel. Most of the recent effort has been directed towards recording the Baily's bead phenomena more accurately, but it is clear that the new techniques must be compared with those used for historical eclipses, so visual observations are still needed for this calibration. Eclipses recorded during this decade will be valuable for comparison with Solar Disk Sextant observations. In addition, analysis of Clementine lidar altimetry promises an improvement in our knowledge of the lunar profile such that the more numerous historical timings made near the central line of total eclipses can be used.

Program listing for Sunday