Using HP-65 Sunrise/Sunset

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(05-10-2017 01:12 AM)Geoff Quickfall Wrote:  ... all rhumb line and great circle formulae require EAST and SOUTH to be -ve.

From Navigation Spreadsheets "Our adopted sign convention marks north latitudes and east longitudes as positive; south latitudes and west longitudes are considered negative; hour angles increase in the westward direction."

The web site is lists the following references:
Jean Meeus, Astronomical Algorithms, Second Edition, Willmann-Bell (2005).
Nautical Almanac, 2009 Commercial Edition, UK Hydrographic Office (2008).
Nautical Almanac, 2010 Commercial Edition, UK Hydrographic Office (2009).
Nautical Almanac, 2011 Commercial Edition, UK Hydrographic Office (2010).
Nautical Almanac, 2012 Commercial Edition, UK Hydrographic Office (2011).
Nautical Almanac, 2013 Commercial Edition, UK Hydrographic Office (2012).
Nautical Almanac, 2014 Commercial Edition, UK Hydrographic Office (2013).
Nautical Almanac, 2015 Commercial Edition, UK Hydrographic Office (2014).
Nautical Almanac, 2016 Commercial Edition, UK Hydrographic Office (2015).
Nautical Almanac, 2017 Commercial Edition, UK Hydrographic Office (2016).
The Astronomical Almanac for the year 2009, The Stationery Office, United Kingdom (2007).
Explanatory Supplement to the Astronomical Almanac, Univ. Science Books (2006).
The American Practical Navigator, (Bowditch 2002).
Thomas J. Cutler, Dutton's Nautical Navigation, 15th Edition, Naval Institute Press (2004).
John Karl, Celestial Navigation in the GPS Age, Paradise Cay Publications (2007).
David Burch, Emergency Navigation, Second Edition, McGraw-Hill (2008).
David Owen Bell, The Celestial Navigation Mystery: Solved, Landfall Navigation (1999).
Hewitt Schlereth, Celestial Navigation in a Nutshell, Sheridan House (2000).
James A. Van Allen, An Analytical Solution Of The Two Star Sight Problem Of Celestial Navigation, Navigation 28 (1), pp. 40-43 (1981).
http://eclipse.gsfc.nasa.gov/SEhelp/deltatpoly2004.html
http://simbad.u-strasbg.fr/
http://www.backbearing.com/

and from Great Circle Mapper FAQ
"There isn't complete agreement on whether latitude or longitude comes first (though usually it's latitude) and it saves confusion to make N/S and E/W explicit.
Besides that confusion, the source data has surprisingly little consistency in the sign conventions for the hemispheres. One might expect negative latitudes to be south of the equator and negative longitudes to be west of the prime meridian. However, an early dump of the FAA data had the sign of the longitude reversed so most of the airports it lists have positive longitudes. (Not all, though. US territories are listed, and GUM, for example, is in the eastern hemisphere, as are a few airports in the far reaches of Alaska's Aleutian Islands.) An even stranger convention was found in the first file from which I distilled the IATA and ICAO data. While longitudes were normal enough, latitudes were relative to the south pole, so the equator was at 90 degrees, not zero, and the north pole was at 180! (This is called a false northing.)"

FINALLY from page 24 of the HP-65 Navigation Pac
"Li = initial latitude (N. positive: S. negative)"
"dj = initial longitude (W. positive: S. negative)"
with respect to program NAV 1-08a Dead Reckoning.

BEST!
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