Cel Nav Coast Guard Questions
The magnitude of three stars is indicated. Which star is the brightest?
Vega + 0.1
Which is an inferior planet?
Venus
Civil twilight begins at 1910 zone time on 20 July 1981. Your DR position at that time is LAT 22°16'N, LONG 150°06'W. Which statement concerning the planets available for evening sights is TRUE?
Venus will have a westerly meridian angle.
A star is observed at lower transit. The line of position derived from this sight is __________.
a latitude line
A latitude line will be obtained by observing a body __________.
at lower transit
In order for a star to be used for a sight at lower transit, the star must __________.
be circumpolar
The navigational triangle uses parts of two systems of coordinates, one of which is the horizon system and the other is the __________.
celestial equator system
When taking stars, those bodies to the east and west will __________.
change altitude rapidly
A marine chronometer should be rewound once every __________.
day
The arc of an hour circle between the celestial equator and a point on the celestial sphere, measured northward or southward through 90°, is the __________.
declination
The Moon rises earlier on succeeding days when the __________.
effect due to change of declination is larger than that due to revolution
The difference between local apparent time (LAT) and local mean time (LMT) is indicated by the __________.
equation of time
The sidereal day begins when the __________.
first point of Aries is over the upper branch of the reference meridian
The center of a circle of equal altitude, plotted on the surface of the Earth, is the __________.
geographical position of the body
A celestial body will cross the prime vertical circle when the latitude is numerically __________.
greater than the declination and both are of the same name
In order to remove index error from a sextant, you should adjust the __________.
horizon glass to make it parallel to the index mirror with the index set at zero
When applying a dip correction to the sighted sextant angle (hs), you always subtract the dip because you are correcting __________.
hs to the sensible horizon
The Sun's center is coincident with the principal vertical circle when __________.
in lower transit
The change in the length of day becomes greater as latitude increases because of the __________.
increased obliquity of the celestial sphere
The GHA of a star __________.
increases at a rate of approximately 15° per hour
An amplitude of the Sun in high latitudes __________.
is most accurate when the Sun's center is observed on the visible horizon
The lunar day is __________.
longer than a solar day
In the navigational triangle, the angle at the elevated pole is the __________.
meridian angle
The difference (measured in degrees) between the GHA of the body and the longitude of the observer is the __________.
meridian angle
The index error is determined by adjusting the __________.
micrometer drum
A sextant having an index error that is "on the arc" has a __________.
negative correction
An azimuth angle for a body is measured from the __________.
observer's meridian
The parallax of the Moon is greatest when the Moon is __________.
on the horizon at perigee
The line of position determined from a sight with an observed altitude (Ho) of 88°45.0' should be __________.
plotted as an arc around the GP of the body
A sextant having an index error that is "off the arc" has a __________.
positive correction
The marine sextant is subject to seven types of errors, four of which may be corrected by the navigator. An error NOT correctable by the navigator is _____________.
prismatic error
The spinning motion of a planet around its axis is called __________.
rotation
A marine sextant has the index arm set at zero and the reflected image of the horizon forms a continuous line with the actual image. When the sextant is rotated about the line of sight the images separate. The sextant has __________.
side error
The celestial coordinate of a star that is relatively constant in value is the __________.
sidereal hour angle
The motion of celestial bodies relative to other celestial bodies is known as __________.
space motion
The same side of the Moon is always toward the Earth, but more than half of its surface has been seen due to libration. Libration in latitude occurs because __________.
the axis of rotation is tilted about 6.5° to the axis of revolution
Index error of a sextant is primarily caused by __________.
the horizon glass not being parallel to the index mirror
A correction for augmentation is included in the Nautical Almanac corrections for __________.
the moon
A semidiameter correction is applied to observations of __________.
the moon
The ecliptic is __________.
the path the Sun appears to take among the stars
The equator is __________.
the primary great circle of the Earth perpendicular to the axis
A sidereal day is shorter than a solar day. This difference is due to __________.
the use of different reference points
When the equation of time is taken from the Nautical Almanac for use in celestial navigation, it is used to determine __________.
time of local apparent noon
Concerning a celestial observation, the azimuth angle is measured from the principal vertical circle to the ____________
vertical circle of the body
90° - Ho = __________.
zenith distance
Yesterday your chronometer read 03h 01m 56s at the 1500 GMT time tick. Today your chronometer read 03h 01m 54s at the 1500 GMT time tick. What is the chronometer rate?
-2s
What is the index error of sextant C? (D050NG )
0'20" on the arc
Your longitude is 179°59'W. The LMT at this longitude is 23h 56m of the 4th day of the month. Six minutes later your position is 179°59'E longitude. Your LMT and date is now __________.
00h 02m on the 6th
The navigator aboard a ship at approximately 165 E longitude observes the Sun at ZT 14-25-04 on 21 September. What is the GMT and Greenwich date of the observation?
03-25-04, 21 September
In the Bay of Fundy, during twilight, you a take sight of Mars. The sextant altitude (hs) is 03°35.5'. Your height of eye is 32 feet and there is no index error. The air temperature is -10°C and the barometer reads 1010 millibars. What is the observed altitude (Ho)?
03°15.8'
The LMT of LAN is 1210. Your longitude is 70°30'E. Which time would you use to enter the Nautical Almanac to determine the declination of the Sun at LAN?
0728
The expression "first magnitude" is usually used to refer only to bodies of magnitude __________.
1.5 and greater
The GHA of the first point of Aries is 315° and the GHA of a planet is 150°. What is the right ascension of the planet?
11 hours
The equation of time is 8m 40s. The apparent Sun is ahead of the mean Sun. If you are on the central meridian of your time zone, the apparent Sun will cross your meridian at __________.
11-51-20 ZT
The equation of time is 12m 00s and the mean Sun is ahead of the apparent Sun. If you are on the central meridian of your time zone, at what zone time will the apparent Sun cross the meridian?
1212
The equation of time is 8m 00s. The mean Sun is ahead of the apparent Sun. If you are 2°W of the central meridian of your time zone, when will the apparent Sun cross your meridian?
1216
What is the geographic longitude of a body whose GHA is 232°27'?
127°33'E
While steering a course of 150°T, you wish to observe the Sun for a speed check. What would the azimuth have to be?
150°T
What is the index error of sextant D? (D050NG )
2'10" on the arc
A first magnitude star is __________.
2.5 times as bright as a second magnitude star
At upper transit, if the zenith distance is 34°, the geographical distance from the observer to a body's GP is __________.
2040 miles
What is the length of the lunar day?
24h 50m 00s
: In 1981, when would Jupiter and Saturn be visible in temperate latitudes for both evening and morning stars?
27 March
What is the index error of sextant B in illustration D050NG? (D050NG )
3'30" off the arc
Because of the reflecting properties of a sextant, if the sextant altitude reads 60° on the limb, the actual arc of the limb from 0° to the 60° reading is __________.
30°
If the Sun's observed altitude is 54°30', what is the zenith distance?
35°30'
If an observer is at 35°N latitude, his zenith is __________.
35°N of the celestial equator
What is the index error of sextant A in illustration D050NG?
4° 20' off the arc
On 25 December 1981 you observe the Sun's lower limb. The sextant altitude (hs) is 4°06.9'. The height of eye is 47 feet and the index error is 1.6' on the arc. The temperature is 19°F. and the barometer reads 1030.8 millibars. What is the observed altitude (Ho)?
4°01.9'
On 16 January 1981, you take a sight of a star. The sextant altitude (hs) is 4°33.0'. The temperature is -10°C, and the barometer reads 992 millibars. The height of eye is 42 feet. The index error is 1.9' off the arc. What is the observed altitude (Ho)?
4°17.0'
A ship is in longitude 54°00'W on a true course of 090°. The ship's clocks are on the proper time zone. At what longitude should the clocks be changed to maintain the proper zone time?
52°30'W
If the Sun's observed altitude is 27°12', the zenith distance is __________.
62°48'
A ship is in longitude 54°00'W on a true course of 270°. The ship's clocks are on the proper time zone. At what longitude should the clocks be changed to maintain the proper zone time?
67°30'W
15° of latitude is equal to __________.
900 miles
When the index and horizon mirrors of a properly adjusted sextant are at an angle of 45° to each other, the arc reads __________.
90°
Which sextant has an index error of 4'20" off the arc? (D050NG )
A
When using horizontal sextant angles of three objects to fix your position, an indeterminate position will result in which situation?
A circle will pass through your position and the three objects
Civil twilight occurs at 0558 zone time on 30 December 1981. Your DR position at that time is LAT 15°02'N, LONG 46°02'W. Which statement concerning the planets available for morning sights is TRUE?
At 0558, Mars can be used for an ex-meridian observation.
Which sextant shown has an index error of 3'30" off the arc? (D050NG )
B.
Which sextant in illustration D043NG reads 29°47.5'? (D043NG )
C
Which sextant shown has an index error of 0'20" on the arc? (D050NG )
C
Which is a nonadjustable error of the sextant?
Centering error
Which sextant in illustration D043NG reads 29°42.5'? (D043NG )
D
There are seven sources of error in the marine sextant. Of the four errors listed, which one is adjustable?
Error of collimation
Yesterday you took a time tick using the 1200 GMT broadcast, and the chronometer read 11h 59m 59s. Today at the 1200 GMT time tick the chronometer read 00h 00m 01s. What is the chronometer error?
Fast 1 second
A position on the Earth has a longitude of 74°10'E. Its celestial counterpart would have a __________.
GHA of 285°50'
Which of the four adjustable errors in the sextant causes side error?
Horizon glass not being perpendicular to the frame
In what order should the following sextant adjustments be made? I. Make telescope parallel to frame of sextant. II. Set horizon glass perpendicular to frame of sextant. III. Make index mirror and horizon glass parallel when index arm is set at zero. IV. Set index mirror perpendicular to frame of sextant
IV, II, III, I
Which of the four adjustable errors in the sextant is the principle cause of index error?
Index mirror and horizon glass not being parallel
Which correction(s) must be applied to an aneroid barometer?
Instrument error and height error
When determining compass error by an azimuth of Polaris, you enter the Nautical Almanac with the __________.
LHA Aries
The First Point of Aries is the position of the Sun on the celestial sphere on or about __________.
March 21
Inferior conjunction is possible for __________.
Mercury
What causes the error of collimation with regards to the four adjustments to a sextant?
Telescope not parallel to the frame
Which statement about the time diagram shown is correct? (D005NG )
The Sun has already passed the lower branch of the observer's meridian
Which statement about the time diagram shown DO08NG is TRUE?
The meridian angle of the Sun is east.
Sidereal hour angle is always __________.
All of the above (measured westward from the hour circle containing the first point of Aries, measured from the point on the celestial sphere occupied by the Sun at the vernal equinox, subtracted from the LHA of the star to obtain the LHA of Aries)
Chronometer error may be found by __________.
All of the above (radio time signal, comparison with a timepiece of known error, applying the prevailing chronometer rate to previous readings)
What is NOT a side of the navigational triangle used in sight reduction?
Altitude
Which is NOT a side of the celestial navigational triangle?
Altitude
