Objectives: 1. To become familiar with the relationships of
the earth to the solar system and the universe.
2. To become familiar with the celestial and
horizon coordinate systems, and how they
relate to the terrestrial coordinate system.
3. To gain a working knowledge of the celestial
and navigation triangles.

Slide3:

Objectives: 4. To become familiar with the concept
involved with a circle of equal altitude.

Elements of the Celestial Sphere:

Elements of the Celestial Sphere

THE CELESTIAL SPHERE:

Infinite radius An imaginary sphere of infinite radius with the earth at it’s center. THE CELESTIAL SPHERE

Zenith - Nadir:

Zenith - Point on the celestial sphere directly above the observers head Zenith - Nadir Nadir - Point on the celestial sphere directly below the observers feet

CELESTIAL BODIES:

PLANETS STARS MOON SUN Celestial bodies are located throughout the celestial sphere. We are interested in the relative positions and motions of these bodies on this imaginary sphere. CELESTIAL BODIES

CELESTIAL POLES:

North Celestial Pole South Celestial Pole CELESTIAL POLES

CELESTIAL EQUATOR:

Also known as the EQUINOCTIAL. It’s the intersection of the extended plane of the equator and the celestial sphere. CELESTIAL EQUATOR

HOUR CIRCLES:

A great circle on the celestial sphere perpendicular to the celestial equator and passing through both celestial poles. HOUR CIRCLES

CELESTIAL MERIDIAN:

A great circle of the celestial sphere, through the celestial poles and the zenith. CELESTIAL MERIDIAN

DECLINATION:

Angular distance of a point on the celestial sphere north or south of the celestial equator Celestial Equator DECLINATION

Parallel of Declination::

Parallel of Declination A circle parallel to the celestial equator. Bodies are considered to travel along the parallel of declination as the earth rotates. Parallel of Declination:

HOUR ANGLE:

HOUR ANGLE The angular distance measured laterally along the celestial equator in a westerly direction through 360º

The Sun at the time of the vernal equinox seems to be located in the constellation Aries: First Point of Aries:

Ecliptic Aries The Sun at the time of the vernal equinox seems to be located in the constellation Aries: First Point of Aries

Sidereal Hour Angle:

SHA SHA Sidereal Hour Angle

SHA of A Star:

Because stars and Aries move at the same rate, the SHA is constant SHA SHA SHA of A Star

GREENWICH HOUR ANGLE:

First meridian GHA GHA SUN GHA GREENWICH HOUR ANGLE

GREENWICH HOUR ANGLE:

SHA OF
ARIES GHA STAR GHA = GHA + SHA GREENWICH HOUR ANGLE

Local Hour Angles:

LHA LHA Local Hour Angles

LOCAL HOUR ANGLE:

SHA LHA LHA LHA = LHA + SHA LOCAL HOUR ANGLE

HOUR ANGLES:

. HOUR ANGLES Sidereal Hour Angle (SHA): Measured in a westerly direction from the hour circle of Aries to the hour circle of the body
Greenwich Hour Angle (GHA): Angular distance measured west of the Greenwich Celestial Meridian.
Local Hour Angle (LHA): Angular distance west of the observers celestial meridian to the body

Location on the Celestial Sphere:

A point on the Celestial Sphere may be identified at the intersection of:
* it’s parallel of declination (Declination)
* it’s hour circle identified by the angular distance west (0º - 360º) of a reference hour circle. Location on the Celestial Sphere

Location of Stars:

The location of Stars are referenced by their Declination and Sidereal Hour Angle. Location of Stars

The Location of Bodies:

The location of the Sun, Moon, planets and First point of Aries are referenced by their Declination and Greenwich Hour Angle. The Location of Bodies

Slide26:

NOW LET’S ADD
MOTION TO
THE SCENE

EARTH MOTION:

EARTH MOTION

DIURNAL MOTION:

IT APPEARS
TO BE
FROM
EAST TO
WEST DIURNAL MOTION

BECAUSE OF THE DIURNALMOTION (EARTH’S ROTATION) :

BECAUSE OF THE DIURNAL MOTION (EARTH’S ROTATION) ALL THE CELESTIAL BODIES SEEM TO MOVE AT ONE RATE, THEREFORE THE GHA’s WILL CHANGE AT ONE RATE AND THE RATE IS:
15DEG -------1HR
360DEG ------24HRS

THE CELESTIALCOORDINATE SYSTEMDESCRIBES THE POSITION OF CELESTIAL BODIES. WE ALSO NEEDED A SYSTEM FROM THE OBSERVER’SPERSPECTIVE:

THE CELESTIAL COORDINATE SYSTEM DESCRIBES THE POSITION OF CELESTIAL BODIES. WE ALSO NEEDED A SYSTEM FROM THE OBSERVER’S PERSPECTIVE

Elements of the Horizon Coordinate System:

Elements of the Horizon Coordinate System

OBSERVER’S HORIZON:

the plane perpendicular to that axis passing through the observer. OBSERVER’S HORIZON

Slide33:

HORIZON ZENITH NADIR

Slide34:

-N- the projection of the poles over the horizon will give us the other coordinate

Slide35:

OBS. HORIZON ZENITH NADIR

CELESTIAL HORIZON:

Another plane parallel to the observer’s horizon but passing through the center of the earth CELESTIAL HORIZON

Slide37:

HORIZON ZENITH NADIR CELESTIAL
HORIZON

Slide38:

HORIZON ZENITH NADIR CELESTIAL
HORIZON

Slide39:

Observer’s Horizon ZENITH NADIR CELESTIAL
HORIZON

Since the radius of the earth is considered negligible with respect to the celestial sphere, the visible horizon is considered to be the same as the celestial horizon.:

Since the radius of the earth is considered negligible with respect to the celestial sphere, the visible horizon is considered to be the same as the celestial horizon.

Slide41:

ZENITH NADIR CELESTIAL
HORIZON

The angular distance above the horizon that a celestial body is measured is called that body’s altitude.:

The angular distance above the horizon that a celestial body is measured is called that body’s altitude.

Slide43:

OBSERVER’S HORIZON CEL. BODY ALTITUDE

Sextant Angle (Hs): The altitude measured by the sextantApparent altitude (Ha): The Sextant Altitude corrected for inaccuracies in the instrument and height of eyeObserved altitude (Ho): All further corrections are applied:

Sextant Angle (Hs): The altitude measured by the sextant Apparent altitude (Ha): The Sextant Altitude corrected for inaccuracies in the instrument and height of eye Observed altitude (Ho): All further corrections are applied

Slide45:

CELESTIAL
HORIZON ALTITUDE VERTICAL
CIRCLE

A Vertical Circle is a great circle on the celestial sphere that passes through the zenith and nadir. It is perpendicular to the celestial (visible) horizon.:

A Vertical Circle is a great circle on the celestial sphere that passes through the zenith and nadir. It is perpendicular to the celestial (visible) horizon.

North Cardinal Point:

The projection of the North pole over the horizon that we measure the true azimuth North Cardinal Point

Slide48:

CEL. BODY ALTITUDE -N- TRUE AZIMUTH

The Principle Vertical Circle is a vertical circle that passes through the north and south celestial poles.:

The Principle Vertical Circle is a vertical circle that passes through the north and south celestial poles.

Slide50:

PRINCIPAL
VERTICAL TRUE AZIMUTH CELESTIAL
HORIZON ALTITUDE Z

Slide51:

THE PLACE WHERE A
LINE LINKING THE
CELESTIAL BODY

Slide52:

PUNCHES IT’S SURFACE AND THE CENTER
OF THE EARTH

Slide53:

THE NAME OF
THAT POINT IS THE GEOGRAPHIC
POSITION GP

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