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 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  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 0 º.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 - 2015  Digital / PC  Ephemerides  Position 0'.15

 NA + AP3270 + GC/Rhumb sailing + Az for compass checks  Calculations  RN Recommended

Times of: • Rise & Set • Twilights • Meridian Passage and •Altitude at Mer.pass

NavPac —RiseSet

NavPac —RiseSet Compass Check Times when • Calculated altitude = 0 ° • Azimuth

NavPac —Findit

An Astronomical Observation

NavPac

Sights

NavPac —Sights Results  Calculations

NavPac —Almanac

NavPac —Finder Rhumb 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?