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NAV 4 > The Equinoctial System of Coordinates > Flashcards

The Equinoctial System of Coordinates Flashcards

1
Q
  • an imaginary sphere surrounding the Earth
A

Celestial Sphere

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2
Q
  • centered around the Earth and depicts all celestial objects as if they were at the same distance away from the Earth
A

Celestial Sphere

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3
Q
  • a practical tool for spherical astronomy, allowing observers to plot positions of objects in the sky when their distances are unknown or unimportant
A

Celestial Sphere

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4
Q

TRUE OR FALSE

* Because astronomical objects are at such remote distances, casual observation of the sky offers no information on the actual distances
A

TRUE

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5
Q

TRUE OR FALSE

* All objects seem equally far away, as if fixed to the inside of a sphere of large but unknown radius, which rotates from east to west overhead while underfoot, the Earth seems to stand still
A

TRUE

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6
Q

TRUE OR FALSE

* For purposes of spherical astronomy, which is concerned only with the directions to objects, it makes no difference whether this is actually the case, or if it is the Earth which rotates while the celestial sphere stands still
A

TRUE

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7
Q
  • either of the two points at which a northward or southward projection of the Earth’s axis intersects the celestial sphere
A

Celestial Pole

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8
Q

TRUE OR FALSE

* The North and South celestial poles are analogous to Earth's geographic poles and are used in determining right ascension in the equatorial coordinate system
A

TRUE

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9
Q
  • the point in the sky about which all the stars seen from the Northern Hemisphere rotate
A

North Celestial Pole

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10
Q
  • The North Star, also called ____________.
A

Polaris

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11
Q
  • the point in the sky about which all the stars seen from the Southern Hemisphere rotate
A

South Celestial Pole

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12
Q

TRUE OR FALSE

    * The Sun is also a star, so the Sun also rotates around the North Celestial Pole
A

FALSE
~ SOUTH CELESTIAL POLE

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13
Q
  • the great circle of the imaginary celestial sphere on the same plane as the equator of Earth
A

Celestial Equator

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14
Q
  • by extension, it is also a plane of reference in the equatorial coordinate system
A

Celestial Equator

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15
Q
  • an abstract projection of the terrestrial equator into outer space
A

Celestial Equator

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16
Q
  • other term of ____________ is equinoctial
A

Celestial Equator

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17
Q
  • a great circle on the celestial sphere representing the sun’s apparent path during the year, so called because lunar and solar eclipses can occur only when the moon crosses it
A

Ecliptic

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18
Q
  • semi-great circles on the celestial sphere joining the celestial poles or projection of the earth’s meridians on the celestial sphere
A

Celestial Meridians

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19
Q
  • cut the equinoctial and the declination circles at 90°
A

Celestial Meridians

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20
Q
  • small circles on the celestial sphere parallel to the plane of equinoctial
A

Declination Circles/Parallels of Declination

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21
Q
  • may also be defined as projection of parallels of latitude on the celestial sphere
A

Declination Circles/Parallels of Declination

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22
Q

The ecliptic intersects the equinoctial at two points called the __________________.

A

equinoctial points

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23
Q
  • the equinoctial point when the Sun appears to cross the equinoctial from South to North
A

First Point of Aries

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24
Q
  • denoted by symbol γ
A

First Point of Aries

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25
Q
  • this occurrence takes place on 21st March, at Vernal Equinox
A
  • First Point of Aries
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26
Q
  • considered as fixed point on the celestial sphere
A

First Point of Aries

27
Q
  • the equinoctial point when the Sun appears to cross the equinoctial from North to South
A

First Point of Libra

28
Q
  • happens on September 22 or 23 each year
A

First Point of Libra

29
Q
  • denoted by the symbol Ώ
A

First Point of Libra

30
Q

TRUE OR FALSE

The First point of Aries and the First point of Libra were named after the constellations in which they once lay.

A

TRUE

31
Q
  • the great circle on the celestial sphere which is equidistant from the celestial poles or whose plane is same as the plane of equator
A

Equinoctial

32
Q
  • the reference plane from which declination of astronomical bodies is measured north or south
A

Equinoctial

33
Q
  • the celestial meridian that passes through Greenwich
A

Celestial Meridian Passing of Greenwich

34
Q

_______________ of all celestial bodies is measured westward from this reference great circle

A

Greenwich Hour Angle (GHA)

35
Q
  • the celestial meridian that passes through first point of Aries
A

Celestial Meridian of First Point of Aries

36
Q

______________ of all celestial bodies is measured with reference to this great circle

A

Sidereal Hour Angle

37
Q
  • the arc of celestial meridian passing through the body contained between the Equinoctial and the body
A

Declination

38
Q
  • may be also defined as arc of celestial meridian or the angle at the center of the earth contained between the Equinoctial and the declination circle passing through the body
A

Declination

39
Q

TRUE OR FALSE

If the body is North of the equinoctial the declination is South

A

FALSE

* If the body is North of the equinoctial the declination is NORTH
40
Q

TRUE OR FALSE

If the body is South of the equinoctial declination is named South

A

TRUE

41
Q

TRUE OR FALSE

* As it is angular measure it is expressed in degrees and minutes and its value is in between 0° to 90° N or S
A

TRUE

42
Q
  • arc of the Equinoctial or the angle at the celestial poles contained between two celestial meridians
A

Hour Angle (HA)

43
Q
  • the arc of the Equinoctial or the angle at the celestial poles contained between the celestial meridian of Greenwich and celestial meridian passing through the body, measured westward from celestial meridian of Greenwich
A

Greenwich Hour Angle (GHA)

44
Q
  • expressed in degrees and minutes and its value is in between 0° to 360°
A

Greenwich Hour Angle (GHA)

45
Q
  • an hour angle the arc of the Equinoctial or the angle at the celestial pole contained between the celestial meridian of the First point of Aries and that through the body, measured westward from Aries
A

Sidereal Hour Angle (SHA)

46
Q
  • an hour angle contained between the celestial meridian of the First point of Aries and the celestial meridian passing through the body, measured eastward from Aries
A

Right Ascension (RA)

47
Q
  • generally expressed in hours, minutes and seconds, instead of, in arc. Since SHA is measured westward and RA eastwards from the same point, the SHA and RA of any body will together always add up to 360°
A

Right Ascension (RA)

48
Q

TRUE OR FALSE

* SHA* + RA* = 360°
A

TRUE

49
Q
  • an hour angle contained between the observer’s celestial meridian and the celestial meridian through that body, measured westward from the observer
A

Local Hour Angle (LHA)

50
Q

If the angle or arc is measured eastward from the observer, it is known as the
_______________ and not LHA.

A

Easterly Hour Angle (EHA)

51
Q

TRUE OR FALSE

LHA* + EHA* = 360°
A

TRUE

52
Q

GIVE THE FORMULAS OF Longitude West GHA BEST

A

~ LHA* = GHA* − Long. (West)
~ GHA* = LHA* + Long. (West)

53
Q

GIVE THE FORMULAS OF Longitude East GHA LEAST

A

~ LHA* = GHA* + Long. (East)
~ GHA* = LHA* − Long. (East)

54
Q

Calculate the LHA of a star whose GHA is 70°, for an observer in longitude 147°E.

A

Solution:

Longitude East GHA Least
LHA*
= GHA* + Long (E)
= 70°+147°
= 217°
= 217°

55
Q

TRUE OR FALSE

The solar system consists of the Sun, the planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto), the planetary satellites (moons), asteroids, comets and meteors.

A

TRUE

56
Q

The most important member of the Solar system is the ________.

A

Sun

57
Q

TRUE OR FALSE

All the planets revolve eastward in elliptical orbits around the sun. The earth also rotates eastward on its axis.

A

TRUE

58
Q

TRUE OR FALSE

  • For the purposes of celestial navigation the earth is assumed to be stationary. Therefore due to eastward revolution of the Earth, the Sun appears to move eastwards on the celestial sphere, in the plane of the Earth’s orbit. the apparent motion of the Sun along the great circle on the celestial sphere, due to the eastward motion of the earth in its orbit.
A

TRUE

59
Q

The great circle on the celestial sphere in the plane of the earth’s orbit is called ___________.

A

Ecliptic

60
Q

TRUE OR FALSE

The great circle on the celestial sphere in the plane of the earth’s orbit is called Ecliptic. It is so called because the Sun, Moon and Earth must be on this plane for a solar or lunar eclipse to occur.

A

TRUE

61
Q

TRUE OR FALSE

The projection of the Moon on the ecliptic from successive positions of the earth in its orbit, appears to constantly move eastwards.

A

FALSE

The projection of the SUN on the ecliptic from successive positions of the earth in its orbit, appears to constantly move eastwards.

62
Q

TRUE OR FALSE

The earth’s axis is inclined to its orbiting plane by about 23° 26.7′. Therefore the equinoctial also makes the same angle with the plane of ecliptic.

A

TRUE

63
Q

The angle at which the plane of ecliptic cuts the equinoctial plane is called _________________.

A

Obliquity of Ecliptic.

NAV 4 (6 decks)

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