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Our Current Astro-Navigation Solutions. Catherine Hohenkerk HM Nautical Almanac Office. UK Hydrographic Office. Astro-Navigation. Sextant, UT1 & the means of “Sight Reduction” Almanac The Nautical Almanac Sight Reduction Tables (SRT) NA’s Concise SRT Marine Navigation : 6 Volumes
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Our CurrentAstro-Navigation Solutions Catherine Hohenkerk HM Nautical Almanac Office UK Hydrographic Office
Astro-Navigation Sextant, UT1 & the means of “Sight Reduction” • Almanac • The Nautical Almanac • Sight Reduction Tables (SRT) • NA’s Concise SRT • Marine Navigation : 6 Volumes • Rapid SRT Navigation: 3 Volumes–AP3270 • Software (or a calculator) • NavPac
The Nautical Almanac (NA) • First published in 1767
Extract: NA left-hand page • 1960, joint pub. with US Naval Observatory
The Nautical Almanac (NP314) • First published in 1767 • Current layout developed in the 50s • 1960, joint pub. with US Naval Observatory • Licensed world wide, via HOs & commercial companies • An almanac + algorithm for reduction of sights + Concise Sight Reduction Tables • An NA is a SOLAS requirement
NA Concise Reduction Tables • Developed in the US (USNO) • Altitude (Hc) to 1' and Azimuth (Zn) 1°
NA Concise Reduction Tables • Developed in the US (USNO) • Altitude (Hc) and Azimuth (Zn) • For use in an emergency • Compact — only 32 pages of tables • Method accurate to ~2' • Complicated to use?
Sight Reduction Tables for • Marine Navigation, NP 401, 6 Volumes • Altitude (Hc) to 0'.1 and Azimuth (Zn) to 0º.1 • Used with an almanac & compatible with NA • Accuracy of method 0'.2 - 0'.3 • Joint publication, HMNAO/UKHO, USNO/NGA • UKHO have ceased printing this volume • US edition (Pub 229) is still available
Rapid Sight Reduction Tables for Navigation • Air Navigation, AP 3270 / NP 303 • 3 Volumes • Altitude (Hc) to 1' & Azimuth (Zn)
AP3270 / NP 303 : Volume 1Selected Stars, 2015 • Method accurate to 0'.5
Rapid Sight Reduction Tables for Navigation • Air Navigation, AP 3270 / NP 303, 3 Vols • Altitude (Hc) & Azimuth (Zn) • Volume1, Selected Stars, “7 best” • Volume 2 & 3, require an almanac • Joint publication of HMNAO, USNO (429) • 2015 edition of Volume 1, published June
NavPac Software : 1986 - 2015 • Digital / PC • Ephemerides • Position 0'.15 • NA + AP3270 + GC/Rhumb sailing + Az for compass checks • Calculations • RN Recommended
NavPac—RiseSet • Times of: • Rise & Set • Twilights • Meridian Passage • and • Altitude at Mer.pass
NavPac—RiseSet Compass Check • Times when • Calculated altitude = 0° • Azimuth
An Astronomical Observation NavPac Sights
NavPac—Sights Results • Calculations
Astro-Navigation for the Future • Web availability? • Software platform independence? • Adobe Acrobat (pdf) e-NA, e-AP3270? • Polar navigation? • UT1/UTC issues? What do you think?