Celestial System of Coordinates

Question 1

CELESTIAL POLES

Answer 1

The celestial poles are the earth’s poles projected until they intersect the celestial sphere.

Question 2

EQUINOCTIAL

Answer 2

Aka: celestial equator - is that great circle of the celestial sphere which is everywhere 90 degrees from the poles or the earth’s equator projected upon the celestial sphere.

Question 3

CELESTIAL MERIDIAN OF GREENWICH

Answer 3

A great circle of the celestial sphere passing from pole to pole and over the Greenwich meridian. All celestial meridians remain fixed over a terrestrial point on earth.

Question 4

LOCAL CELESTIAL MERIDIAN

Answer 4

Is the observer’s meridian projected upon the celestial sphere.

Question 5

THE HOUR CIRCLE

1. Declination
2. Polar Distance

Answer 5

Is the great circle which passes from pole to pole through the body and moves with the body.

1. Is the angular distance a body is N or S of the celestial equator. It is measured along the hour circle of the body from 0-90 deg.
2. Is the angular distance of a celestial body, measured along the hour circle of the body from the elevated pole to the body.

Question 6

GREENWICH HOUR ANGLE (GHA)

Answer 6

Is the arc

Question 7

LONGITUDE

Answer 7

Is the arc of the equator measured from the Greenwich Meridian from 0-180 deg E/W to the meridian of a terrestrial position.

Question 8

LOCAL HOUR ANGLE (LHA)

Answer 8

The angle measured WESTWARD from the observer’s meridian to the Hour Circle of the Body 0-360 deg.

Question 9

MERIDIAN ANGLE

Answer 9

The arc of the celestial equator or the angle at the pole measured between the local celestial meridian and the hour circle of the body measured 0-180 E/W.

Question 10

ECLIPTIC

Answer 10

The path the sun appears to take among the stars, inclined to the Equinoctial at 23deg26’.

Question 11

FIRST POINT OF ARIES / VERNAL EQUINOX

Answer 11

Point where the sun crosses the celestial equator as it moves from South to North. Mar21 and marks first day of spring for an observer in Northern Latitudes.

Question 12

SUMMER SOLSTICE

Answer 12

The sun reaches its max Northerly declination of about 23deg26’. Occurs about Jun21 and marks first day of summer for observer’s in Northern Latitudes.

Question 13

AUTUMNAL EQUINOX

Answer 13

Point where the sun crosses the celestial equator on its journey Southward. Marks the first day of autumn for observer’s in Northern Latitudes, about Sep23.

Question 14

WINTER SOLSTICE

Answer 14

Point where the sun reaches its max Southerly Declination at 23deg26’. Occurs about Dec21 and marks first day of winter for observer’s in Northern Latitudes.

Question 15

HOUR CIRCLE OF ARIES

Answer 15

Is a great circle passing from pole to pole and through the FPA which is considered to be a body.

Question 16

SIDEREAL HOUR ANGLE (SHA)

Answer 16

Angle measured WESTWARD from the FPA to the Hour Circle of the Body, 0-360deg