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First Semester (2nd Year) > CELNAV (MIDTERM) > Flashcards

CELNAV (MIDTERM) Flashcards

1
Q

This is the correction to the sextant altitude applied to the visible horizon to obtain the
sensible horizon
A.Dip
B.Refraction
C. Parallax
D. Semi-diameter

A

A.Dip

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2
Q

One complete turn of the drum of the sextant moves the index arm along the arc by:
A.30 secs
B. 1 min.
C.30 mins.
D. 1 degree

A

D. 1 degree

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3
Q

When the index mirror and the horizon mirror of the sextant are parallel, the sextant should read:
A.0°
B.60°
C.90°
D.120°

A

A.0°

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4
Q

What do you call the error in the observed altitude of the sun, which results from the
observer being on the surface of the earth not at its center?
A.Dip
B.Parallax
C. Semi-diameter
D. Refraction

A

B.Parallax

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5
Q

Which of the four adjustable errors in the sextant principal cause of index error?
A. index mirror not perpendicular to the frame
B. index mirror and horizon glass not parallel
C. horizon glass not perpendicular to the frame
D. telescope not parallel to the frame

A

B. index mirror and horizon glass not parallel

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6
Q

The Moon appears larger in diameter at the zenith than when near the horizon. What is this called?
A. Augmentation
B. Parallax
C. Refraction
D.Semi-diameter

A

A. Augmentation

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7
Q

The optical principle of a marine sextant is when a ray of light is reflected from a plane surface,
the angle of reflection is equal to the
A. Angle of repose
C. Angle of incidence
B. Angle of refraction
D. Angle of scattered light

A

C. Angle of incidence

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8
Q

The correction of atmospheric refraction as applied to the observed altitude of a body
A. depends only on atmospheric conditions and is independent of altitude
B. decreases with altitude
C. increases with altitude
D. is negligible and can be ignored

A

C. increases with altitude

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9
Q

Which of the following is an adjustable sextant error?
A. Index error
B. Perpendicularity error
C. Side error
D. All of these

A

D. All of these

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10
Q

It is a plane which passes through the observer’s eye and is at the right angles to the
vertical of the observer.
A. Rational horizon
B. Apparent horizon
C. Sensible horizon
D. Geoidal horizon

A

C. Sensible horizon

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11
Q

It is the angle actually measured between the body and the visible horizon
A. Apparent altitude
B. Sextant altitude
C. Observed altitude
D. True altitude

A

C. Observed altitude

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12
Q

What is “side error” on a marine sextant?
A. When the horizon glass/mirror is not perpendicular to the plane of the sextant
B. When the telescope collar is not perpendicular to the plane of the sextant
C. When the index mirror is not perpendicular to the plane of the sextant
D. When the index mirror and the horizon glass/minor are not parallel at all times

A

A. When the horizon glass/mirror is not perpendicular to the plane of the sextant

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13
Q

The movable arm of the sextant is the:
A. index arm
B. tangent screw
C. micrometer drum
D. release vernier

A

A. index arm

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14
Q

The error remaining in the sextant after the navigator has removed side error perpendicularity error
and collimation error is.
D. prismatic error
A. index error
B. centering error
C. graduation error

A

A. index error

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15
Q
  1. It is a function of LHA of the First Point of Aries and latitude and is the excess of the second order
    term over its mean value for latitude 50°.
    A. a0
    B. a1
    C. a2
    D. azimuth
A

B. a1

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16
Q

It is a line drawn on a chart at right angle to the true bearing of the body under observation
the position of the ship being somewhere on the line.
A. longitude line
C. geographical position line
B. bearing line
D. celestial position line

A

D. celestial position line

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17
Q

You live at a latitude of 73° N. What is the angle between the northern horizon and the north
celestial pole?
A. 73°
B. 27°
C. 17°
D. 23 ½°

A

A. 73°

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18
Q

It is a function of the LHA of the First Point of Aries and of date and is a correction to the first
term for the variation of the SHA and declination during the year.
A. 30
B. a1
C. a2
D. azimuth

A

C. a2

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19
Q

If the north celestial pole appears on your horizon, what is your latitude?
A. 90° N
B. 90° S
C. 0°
D. The latitude of the observer can not be determined from the information given.

A

A. 90° N

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20
Q

You live at a latitude of 39° S. What is the angle between the southern horizon and the south celestial
pole?
A. 45°
B. 23.5°
C. 39°
D. 51°

A

C. 39°

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21
Q

Find the longitude of the observer from the following given: GHA of the star 112° 45’
LHA of the star 333° 45’, latitude of the observer 220 55’ N.
A. 139°00’ W
B. 089 degrees 50’ E
C. 089° 50’ W
D. 1120 45’ F

A

A. 139°00’ W

22
Q

Find GHA of Aries from the following given: longitude of the observer 025° 38’ W, SHA of
the star 218° 10’, LHA of the star 045° 30’.
A. 289° 18’
B. 070° 42’
C. 2120 58’
D. 267° 07’

A

A. 289° 18’

23
Q

On Sept. 12, at GMT 10h35m in longitude 057* 58’ W, the Ho of star Polaris was 3550’. The correction
values from the Polaris Tables: A0 = 122.1’, A1 = 0.4’, A2 =0.9’ Find the latitude of the observer.
A. 36 13.4’ N
B. 35’13.4’ N
C. 37°13.4’ N
D. 36°13.4’ S

A

A. 36 13.4’ N

24
Q

You are in longitude 175° W and heading 270° where do you change clocks?
A. 172030’ E
B. 165° 30’ E
C. 172°30’ W
D. 180 degrees

A

D. 180 degrees

25
Q

A body will be observed at lower transit only :
A. during daylight hours
B. during summer time
C. if the body is circumpolar
D. when latitude is greater than declination and are of the same name

A

D. when latitude is greater than declination and are of the same name

26
Q

This is the correction to the sextant altitude applied to the visible horizon to obtain the sensible horizon
A. Dip
B. Refraction
C. Parallax
D. Semi-diameter

A

A. Dip

27
Q

If the observer is at 5° South and the sun’s declination is 10° North, what will be the
bearing of the body during meridian passage?
A. 180 degrees T
B. 15 degrees South
C. 10 degrees North
D. 000 degrees T

A

B. 15 degrees South

28
Q

It is a function of LA of the First Point of Aries and latitude and is the excess of the second order
term over its mean value for latitude 50°.
A. a0
B. a1
C. az
D. azimuth

A

B. a1

29
Q

What is the approximate latitude of the observer in the diagram below?
Celertial
A. 90°
B. N 00°
C. 50° N
D. 50° S

A

50 N

30
Q

What is the latitude of a place where the sun is at the horizon at midnight of December 21 or 23?
A. 230 27’ N
C. 66033° N
C. 66° 33’ S
D. 23* 27’ S

A

D. 23* 27’ S

31
Q

It is a line drawn on a chart at right angle to the true bearing of the body under observation
the position of the ship being somewhere on the line.
A. longitude line
B. bearing line
C. geographical position line
D. celestial position line

A

D. celestial position line

32
Q

Meridian angle is equal to Local Hour Angle when celestial body is:
A. rising not to exceed 1800
B. rising not to exceed 360°
C. setting not to exceed 180°
D. setting not to exceed 360°

A

C. setting not to exceed 180°

33
Q
  1. The amplitude will be numerically equal to the declination only when:
    A. Latitude is zero
    B. Latitude is 900
    C. Altitude is zero
    D. Altitude is 900
A

A. Latitude is zero

34
Q

Convert azimuth angle S 82.8° E to amplitude.
D. S07.29 E
B. E82.80 S
C. E 07.2° S
A. $82.80 E

A

C. E 07.2° S

35
Q

What is the zenith distance of the sun at theoretical sunrise and sunset?
A. 108°
B. 102°
C. 90°
D. 96°

A

C. 90°

36
Q

What is the approximate latitude of the observer in the diagram below?
South
Celestial
A 20° N
Pole
B.
20° S
C.
70° N
D. 70° S

A

20 S

37
Q

At lower transit, the body’s altitude is at its minimum bearing North or South. What will be the LHA?
B. 090 degrees T
C. 270 degrees T
D. 060 degrees T
A. 180 degrees

A

A. 180 degrees

38
Q

If the altitude of the elevated pole is 90, therefore:
A. The Polar distance is also 90
B. The Declination is indeterminate
C. The latitude of the observer is at the pole
D. The Polar distance equals the declination

A

C. The latitude of the observer is at the pole

39
Q

You live at a latitude of 73° N. What is the angle between the northern horizon and the north
celestial pole?
A. 73°
B. 27*
C. 17°
D. 23 ½°

A

A. 73°

40
Q

Find the azimuth angle of the celestial body when the amplitude is E 16° 15.9’ S.
A. E 16° 15.9’ S
B. S 73* 44.1 E
C. S 16° 15.9’ E
D. 1630 44.1’

A

B. S 73* 44.1 E

41
Q

It is a function of the LHA of the First Point of Aries and of date and is a correction to the first
term for the variation of the SHA and declination during the year.
A. ao
B. a
C. a2
D. azimuth

A

C. a2

42
Q

If the north celestial pole appears on your horizon, what is your latitude?
A. 90° N
B. 90° S
C. 0°
D. The latitude of the observer can not be determined from the information given.

A

A. 90° N

43
Q

You live at a latitude of 39° S. What is the angle between the southern horizon and the south
celestial pole?
A. 45°
B. 23.5°
C. 39°
D. 51°

A

C. 39°

44
Q
  1. What is the angular distance of the sun from the zenith of the observer at noon of June 21
    or 23 if the observer is navigating along the Tropic of Cancer?
    A. 0°
    B. 230 27°
    C. 66°33’
    D. 90 degrees
A

A. 0°

45
Q

How far and where will the sun be from the zenith of the observer at noon of December 21
or 23 if the observer is navigating along the Tropic of Cancer?
A. 23° 27’ south of the observer
B. 46° 54’ south of the observer
C 66°33” south of the observer
D. 230 27’ north of the observer

A

D. 23* 27’ north of the observer

46
Q

The moon appears larger in diameter at the zenith than when near the horizon. What is this called?
A. Augmentation
B. Parallax
C. Refraction
D. Semi-diameter

A

A. Augmentation

47
Q

The body would be at the nadir at lower transit when:
A. Latitude is of the same name and numerically equal to declination.
B. Latitude is of contrary and numerically equal to the declination.
C. Latitude is of the same name and numerically less than the declination.
D. Latitude is of the same name and numerically greater than the declination.

A

B. Latitude is of contrary and numerically equal to the declination.

48
Q

Seen from the northern latitudes (mid-northern hemisphere), the star Polaris
A. is never above the horizon during the day.
B. always sets directly in the west.
C. is always above the northern horizon.
D. is the brightest star in the sky.

A

C. is always above the northern horizon.

49
Q
  1. In the orthographic projection of the horizon system of coordinates, when the body rises to
    the right of the Prime Vertical (PV), the amplitude is named:
    A.E: N
    B. E:S
    C. W: N
    D. W: S.
A

A. E: N

50
Q

During meridian passage, the LHA and meridian angle of the body is zero. What is
its altitude?
A. maximum altitude
B. minimum altitude
C. about 90 deg.
D. equal to your latitude

A

D. equal to your latitude

51
Q

The type of sphere when the observer is in latitude 60° N.
A. Right sphere
B. Parallel sphere
C. Oblique sphere
D. Circular sphere

A

C. oblique sphere

First Semester (2nd Year) (14 decks)

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