Celestial Navigation

VE3WIO

Learning Objective

• Thoroughly confuse people about Celestial Navigation

• Convince people that they should never leave land

• Unless they want a life changing experence

Agenda

• Lighthouse • GP • Almanac • Sextant • Azimuth & Elevation

Lighthouse Circles of position

Altitude

Altitude

One has to see the HORIZON

Celestial COP

GP

• Geographic Position – Location on the surface of the earth of a line

between the centre of the earth and the centre of the body

Almanac • Geographical Position, hourly (GP)

– Greenwich Hour Angle, (GHA) – Declination, (Dec) – Universal Coordinated Time, (UT)

• UT Hourly (GP) of the Sun, Moon, Major Planets, Major Stars

• Size of Sun and Moon, upper and lower limb (UL & LL) • Brightness of stars and planets, (Mag) • Translation of height of eye to angle below horizon, (DIP) • Daily nautical and civil twilights • Sun and moon rise and set

From the Almanac Where is the Sun

Sextant

Taking a Sight

• Telescope aimed at the horizon • Index arm adjusted to the appropriate angle • Sun and Moon decide on top (upper limb) or bottom

(lower limb)

Split Field

Time

• Accurate time is needed to look up celestial body’s GP in the Nautical Almanac

• Error of 1 second in time leads to an error of up to 0.25 nm in LOP

• Celestial bodies - tabulated in the Almanac according to UT

• Reference CHU, WWV • Video “Longitude”, John Harrison, a self-educated

English clockmaker, invented the marine chronometer, • 1 minute of Latitude = 1nm

Other things to consider

• Where do you think you are • Height of eye above water correction “DIP” • Watch error • Time zone • Parallax / Refraction • Sextant error “Index Error”

Collecting Data

Time and Date

Body and estimated location

Sextant

Almanac

RESULTS

Need to do another sight 0834 hrs and 1346 hrs local (UT-5)