NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Refraction
From: Marcel Tschudin
Date: 2005 Aug 19, 19:24 +0300
From: Marcel Tschudin
Date: 2005 Aug 19, 19:24 +0300
Dear D.H. Sadler From wherever you may read this mail: Felicitation for your table "CORRECTIONS TO BE APPLIED TO OBSERVED ALTITUDE, Refraction" which you, together with your colleagues, compiled and published 1952 in the Journal of the Royal Institute of Navigation; this table became really a contribution of enduring value. I just wanted to let you know that what you published more than half a century ago is still being published in regular intervals by the National Imagerie and Mapping Agency in their Sight Reduction Tables for Air Navigation, Pub. No. 249 and, from what I was told, also in the Air Almanac. Your table was by the way the only publication I was able to find, when I was searching these days of the year 2005 for published refraction values for negative altitudes. May be you know that we have come here in to the age of computers. But believe it or not, this could not change anything to what you derived by hard manual work. From what I notice, not a single figure has been changed in the meantime. Could it be, that these days, where everybody has a computer, one concluded, that it would not being worth updating your table since everybody would now be able to calculate these values and, as a result, your table was just left there for historical reasons? Or, was your table left in these handbooks for all those enthusiastic hobby-sailors, who still like to navigate with sextant and tables? Yes, you might not know that navigation became now less a profession and more a hobby. Technique has so much advanced, that with the help of some satellites circulating around our planet and with some fancy electronic equipment anyone can be now a professional navigator, finding even out whether he/she is in the bedroom or in the living room (just in the case he/she would not know it). Your table is in my view more than just a historical relict. I find it a useful collection of benchmark values. Benchmarks are very helpful to all those who try to calculate something in order to have a reference for their results. Since with the help of computers it is now possible to do more refined calculations, I would like to ask you for your kind permission, for having your table updated by using the newest calculation procedures and also using the newest atmospheric models. As you know, there want be drastic changes, only some refinements of the results which you and your colleagues already obtained. Those new derived data would then however correspond to the calculation capabilities and the knowledge of this time at the beginning of the third millennium. Thank you for your attention. Awaiting your reply, I remain Yours sincerely Marcel E. Tschudin