Difference between revisions of "Terrestrial refraction"
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for refractions for zenith distances greater than about 80� may | for refractions for zenith distances greater than about 80� may | ||
be considered more curious than useful’’'' | be considered more curious than useful’’'' | ||
| + | |||
| + | Citing d, Ivory (1823) | ||
| + | ‘‘The refractions are ... affected by circumstances of which the observer has no intimation, and which | ||
| + | cannot enter into any theory. The real causes of such anomalies | ||
| + | is [sic] undoubtedly the irregular changes that take place in the | ||
| + | remote parts of the atmosphere, which are not indicated by the | ||
| + | barometer or the thermometer.’’<ref>Ivory, James. "XXVIII. On the astronomical refractions." Philosophical Transactions of the Royal Society of London 113 (1823): 409-495.XXVIII. </ref> | ||
| + | |||
Citing | Citing | ||
| − | + | Himself | |
"Refraction within about 5° of the horizon is so variable that | "Refraction within about 5° of the horizon is so variable that | ||
no a priori formula or table can be expected to give accurate | no a priori formula or table can be expected to give accurate | ||
| − | values there."<ref>Young, Andrew T. "Sunset science. IV. Low-altitude refraction." The Astronomical Journal 127.6 (2004): 3622.: https://iopscience.iop.org/article/10.1086/420806/pdf</ref> | + | values there." |
| + | |||
| + | "Refraction within about 5° of the horizon is so variable that | ||
| + | no a priori formula or table can be expected to give accurate | ||
| + | values there; the local lapse rate and thickness of the boundary | ||
| + | layer above the observer must be known. " | ||
| + | |||
| + | "At and below the astronomical horizon, the refraction depends | ||
| + | primarily on atmospheric structure below the observer and | ||
| + | varies so much (tens of minutes, or even several degrees) that | ||
| + | only very crude predictions can be made." | ||
| + | |||
| + | <ref>Young, Andrew T. "Sunset science. IV. Low-altitude refraction." The Astronomical Journal 127.6 (2004): 3622.: https://iopscience.iop.org/article/10.1086/420806/pdf</ref> | ||
Revision as of 06:31, 20 April 2020
place holder DRAFTING
Uncertainty, precision, model accuracy, predictive power
"Every one conversant with nautical astronomy is aware that some uncertainty always attends observations made with the natural horizon, from the varying amount of the dip occasioned by terrestrial refraction. The cause of these variations is very obscure. The best authorities seem to regard differences of temperature in the air and water as the sole cause of the irregular density of the lower strata of the atmosphere on which the varieties of the dip depend. It is known that, in general, when the water is warmer than the air, the dip is greater than that given in the tables; and that when the water is colder than the air, the dip is less. But cases occur where the deviations from the tables are found to bear little relation, at least in amount, to the relative temperatures of the air and water. Some other property of the atmosphere must, therefore, be sought after, by the influence of which the effects of temperature are modified."[1]
Young
Citing {Brinkley, J. 1815, Trans. R. Irish Acad., 12, 77}
"It is well known to those conversant in observations
made with good instruments that near the horizon an irregularity in refraction hitherto unexplained shews itself."
‘‘it is not likely the irregularities will ever be
submitted to any law, and investigations respecting formulae
for refractions for zenith distances greater than about 80� may
be considered more curious than useful’’
Citing d, Ivory (1823) ‘‘The refractions are ... affected by circumstances of which the observer has no intimation, and which cannot enter into any theory. The real causes of such anomalies is [sic] undoubtedly the irregular changes that take place in the remote parts of the atmosphere, which are not indicated by the barometer or the thermometer.’’[2]
Citing
Himself "Refraction within about 5° of the horizon is so variable that no a priori formula or table can be expected to give accurate values there."
"Refraction within about 5° of the horizon is so variable that no a priori formula or table can be expected to give accurate values there; the local lapse rate and thickness of the boundary layer above the observer must be known. "
"At and below the astronomical horizon, the refraction depends primarily on atmospheric structure below the observer and varies so much (tens of minutes, or even several degrees) that only very crude predictions can be made."
References
- ↑ W. Kelly “On the dip of the horizon, and mirages of the Gulf and River St. Lawrence,” Nautical Mag. (London) 15, 393–398 (1846) https://aty.sdsu.edu/bibliog/bibliog.html
- ↑ Ivory, James. "XXVIII. On the astronomical refractions." Philosophical Transactions of the Royal Society of London 113 (1823): 409-495.XXVIII.
- ↑ Young, Andrew T. "Sunset science. IV. Low-altitude refraction." The Astronomical Journal 127.6 (2004): 3622.: https://iopscience.iop.org/article/10.1086/420806/pdf
