Horizon System Of Coordinates

Question 1

ZENITH

Answer 1

Point directly overhead of observer on Celestial Sphere

Question 2

NADIR

Answer 2

Point directly below observer on the Celestial Sphere

Question 3

CELESTIAL HORIZON

Answer 3

Great circle of the Celestial Sphere which is everywhere 90deg from the Zenith and Nadir.

Question 4

VERTICAL CIRCLE

Answer 4

VC of the Celestial Sphere which passes through the Zenith and Nadir and the Body.

Question 5

ALTITUDE

Answer 5

Angle measured along the VC from the horizon to the body.

Question 6

CO-ALTITUDE (CO-ALT)

Answer 6

Or Zenith distance is the angle measured along the VC fromm the Zenith to the Body.

Question 7

PRIME VERTICAL CIRCLE

Answer 7

VC which intersects the horizon at the E/W points

Question 8

AZIMUTH

Answer 8

Arc of the horizon or the angle at the Zenith measured from the North point clockwise from 0-360deg, (to the VC of the body).

Question 9

AZIMUTH ANGLE

Answer 9

Arc of the horizon or the angle at the Zenith, measured between either the North point or South point from 0-180deg E/W, to the VC of the Body. Must have a prefix - suffix. Prefix is determined by the observer’s latitude; Suffix is determined by the name of the meridian angle.

Question 10

PARTS NEEDED FOR NAVIGATIONAL TRIANGLE

Answer 10

Zenith
Nadir
Celestial Horizon
VC
Celestial poles
Equinoctial
Hour Circle.

Question 11

SIDES OF NAVIGATIONAL TRIANGLE

Answer 11

Observer’s Celestial Meridian - CoLat

Hour Circle of the Body - CoDec or Polar Distance

VC of the Body - CoAlt or Zdistance

Question 12

ANGLES IN THE NAVIGATIONAL TRIANGLE

Answer 12

Meridian Angle
Azimuth Angle
Parallactic Angle