Our CurrentOur CurrentAstro-Navigation SolutionsAstro-Navigation Solutions

Catherine Hohenkerk

HM Nautical Almanac Office

UK Hydrographic Office

Astro-NavigationSextant, 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 right-hand page

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

Altitude (Hc) to 1' and Azimuth (Zn) 1°

Developed in the US (USNO)

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 1 Selected Stars, 2015

Method accurate to 0'.5

AP3270 / NP 303, Volume 2 & 3

Rapid Sight Reduction Tables for Navigation

Air Navigation, AP 3270 / NP 303, 3 Vols Altitude (Hc) & Azimuth (Zn) Volume 1, 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 - 2015Digital / PCEphemeridesPosition 0'.15NA + AP3270 +

GC/Rhumb sailing + Az for compass checks

CalculationsRN

Recommended

NavPac—RiseSet

Times of:

• Rise & Set

• Twilights

• Meridian Passage

and

•Altitude atMer.pass

NavPac—RiseSet Compass Check

Times when

• Calculated altitude = 0°

• Azimuth

NavPac—Findit

An Astronomical Observation

NavPacSights

NavPac—Sights Results

Calculations

NavPac—Almanac

NavPac—FinderRhumb Line/Great Circle Routes

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?