Astronomy and the limits of vision

Forecasting Andean rainfall and crop yield from the influence of El Niño on Pleiades visibility

“…The reanalysis data set 26 indicates that the surface relative humidity of about 60±70% increases by about 5±10% in warm years. Standard formulas 27 indicate that this increase would alter apparent magnitude by about 0.1, a level too small to be appreciated by the naked-eye observer. We conclude that the signi®cant changes in visibility are attributable to changes in high cloud alone.…”

The Crossover of the Sun and the Moon

“…[1] This criterion gave similar results when compared with Odeh's criterion, 14 which is a development of Yallop's 15 adaptation of several methods, 16 using topocentric coordinates. Even if these empirical methods do not provide the same degree of accuracy as the modern theoretical model presented by Shaeffer that reduces to half the uncertainty zone of the lunar dateline (the geographical locus of points on which the probability of sighting the crescent is 50%), 17 the authors considered that for the purpose of the present work their accuracy was enough. Even Shaeffer recognized that from the modern empirical criteria, Yallop gave the best results.…”

A Study of the Simple Geometrical Relationship of the Main Monuments of Giza and a Possible Connection to Stars

“…Practical tests demonstrate that few people possess an observational accuracy better than 3.5 arc minutes, and in addition to this a so-called "smearing" effect has to be taken into account when observing near the horizon due to the greater mass of air through which light travels (Schaefer, 1993). Thus an observer at the Convergence Point would have seen a match of stars to pyramids of great visual accuracy, adding weight to the authors' opinion that this ground-sky synchronisation was a deliberate act created as part of Khufu's pyramid complex at Giza.…”