Celestial Navigation (13 Pts)

Altitude Intercept Method

Use the AP, draw a line through the AP along the Azimuth Angle; compute the difference between Ho and Hc to determine distance the AP from intercept in nautical miles; Ho > Hc, intercept is towards GP; Hc > Ho, intercept is away GP

Nav Triangles

When the Celestial Triangle is pulled down to the surface of the Earth

Celestial Triangle

a combination of the Celestial Sphere and Horizon Coordinates

Visible Horizon is?

a plane parallel to the Celestial Horizon and runs tangent to the surface of the Earth (what we actually see)

Celestial Horizon is?

a plane passing through the center of the Earth perpendicular to the observers location

Zenith

directly above the observer-- 90 degrees altitude

Nadir

directly below the observer extended through the center of the Earth

Azimuth

horizontal direction of a point on the celestial sphere; true bearing to the Celestial Body's Geographical Position (GP)

Horizon Coordinate System

system based on the Observer's Location

Sight Reduction is?

the calculation and comparison; yields a Celestial LOP

Nav Triangle is formed by...?

vertices of the Pole (North/South), the Assumed Position (AP), and the celestial body's Geographical Position (GP)

Hs

Height Sextant

Celestial Triangle is formed by..?

the vertices of the elevated Celestial Pole (Pn or Ps), the Observers Zenith (Z) and the celestial body's position

Arcs of the Celestial Triangle

Codeclination and Colaltitude and Colatitude

Arcs of the Nav Triangle

Codeclination and Colaltitude and Colatitude

Ha

Height Apparent

Hc

Height Computed/ Calculated

Ho

Height Observed

What is Celestial Theory?

It is visual navigation; Celestial bodies are used as visual NAVAIDs; it is used to derive an LOP from a celestial sight.

Why use Celestial?

It provides a reliable backup to electronic forms of navigation and an understanding of the principles of celestial navigation; it will make you aware of your position in relation to the Earth and the heavens.

How does CELNAV work?

Nautical Almanac and Sight Reduction tables are used to calculate the position; "altitude" can be calculated based on our DR Position and then compared to observed "altitude" taken by Sextant Observation

Celestial Counterpart to Terrestrial

North Celestial Pole (Pn); South Celestial Pole (Ps); equinoctical; Declination; Greenwich Meridian; Hour Angles (Greenwich (GHA); Local (LHA); Sidereal (SHA))

Terrestrial

North Pole; South Pole; Equator; Latitude; Prime Meridian; Longitude

Celestial Navigation used to:

Predict sunrise/sunset and moonrise/moonset; determine gyro error (Azimuth of Sun/ Azimuth of Polaris (North Star))

What software/program does the US Navy use?

STELLA; Royal Navy uses NAVPAC

Hour Angles (Three): angular distance measured westward from a reference point

Sidreal Hour Angle (SHA)- used to determine position of Stars and Planets; Greenwich Hour Angle (GHA); Local Hour Angle (LHA)

Circles of Equal Altitude

An observation of a Celestial Body will yield a Circle of Equal Altitude, and the observer will know that they are somewhere on that circle. -3 LOPs = fix -plotting multiple Circles of Equal Altitude can determine position