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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
T & B Corrections
From: Chuck Taylor
Date: 2000 Nov 09, 7:58 AM
From: Chuck Taylor
Date: 2000 Nov 09, 7:58 AM
The T & B (Temperature & Barometric Pressure) corrections in the Nautical Almanac are provided for occasions when temperature and barometric pressure differ from the "standard" temperature of 10 degrees Celsius (50 degrees Fahrenheit) and 1010 millibars (29.83 inches of mercury). They are applicable mostly to low-altitude sights and allow for the fact that refraction can vary with T & B. An aeronautical engineer friend of mine tells me than "Standard Temperature and Pressure" in his world are 15 degrees Celsius (59 degrees Fahrenheit) and 1013 millibars (29.92 inches of mercury). Does anyone know the logic for selecting 10 degrees Celsius and 1010 millibars as the basis for the refraction tables? There must be some historical reason, but I can't find it in Bowditch. Chuck Taylor Everett, WA, USA
