Slawomir K. Grzechnik wrote: > Where did you get these formulae from? I have used for ages another one > > dip['] = 1.76 * sqrt( a[m] ) or its older equivalent > dip['] = 0.97 * sqrt( a[ft] ) > > where a is height of eye and units are given in bracket angles and ' stands > for minute of arc rather than foot. The formulae include Earth curvature and > mean terrestrial refraction for standard pressure 760 mm Hg (1013.2 mb or hP) > air temp. +10 C water temp. +10 C (guess formulae may be used on land as > well) > > The result should be corrected for temperatures and pressure if you are able > to measure those, not that hard after all. "My" formulae are cited in manuals > of navigation and Alamanachs together with tables and correction tables for > temperatures and pressure. So where did you get "yours" from?
To complicate matters even further, the revised edition of the _Explanatory Supplement to the Astronomical Almanac_ (1992) in fact recommends the following correction for computing the true altitude of a celestial body near the horizon (cf. p. 484): - 2.12 * sqrt(a[m]) or - 1.17 * sqrt(a[ft]) As explained on pp. 488-489, when calculating the true altitude of a celestial body near the horizon, in addition to ordinary dip (for which the constants 1.76 [m] or 0.97 [ft] are cited) an additional correction of 0.37 * sqrt (a[m]), or 0.20 sqrt(a[ft]), has to be applied. ================================================================ * Robert H. van Gent * Tel/Fax: 00-31-30-2720269 * * Zaagmolenkade 50 * E-mail: [EMAIL PROTECTED] * * 3515 AE Utrecht * Home page (under construction): * * The Netherlands * http://www.fys.ruu.nl/~vgent/ * ================================================================
