AVS Flashcards
What is your latitude if you are sailing in the northern hemisphere while the sun is in the southern hemisphere, with the sextant angle taken during meridian passage of 42°06.7’ and the declination 5°24.9’?
53°18.2’N
What is formed by arcs of a celestial meridian, an hour circle, and a vertical circle, and its vertices are the elevated pole, the zenith, and a point on the celestial sphere?
Navigational triangle
Which coordinate is a vertical circle through the east and west points of the horizon and is perpendicular to the principal vertical circle?
D
Which publication is updated annually?
Nautical Almanac
What is the plane of the sensible horizon if the observer is at the center of the Earth?
Celestial horizon
Your vessel is at sea on June 22, 2023 with DR position 32°30’ N 061°55’W . As an OOW, you are taking your position by meridian passage at 1202H with the sun’s sextant altitude of 80°55.8’ in the same hemisphere. With the following date, solve each item to determine your latitude. How much is the zenith angle?
8°51.4’
What is perpendicular to the plane of the instrument when properly adjusted?
B
What is the purpose of the part indicated by letter “E”?
To receive the image from the index mirror and reflect it back to the observer through the telescope
Which chart projects the equatorial stars of the eastern hemisphere?
B
Which is NOT TRUE about meridian passage?
This takes place always at precisely 12 noon.
Analyze which star has the azimuth of 230°
Altair
What is the sextant altitude of the body based on this reading?
29°42.5’
Which chart projects the stars with declination between 30° and 90° south?
B
Which star is used as a preference to find a position that gives 90° altitude, which is the same as your latitude when it is directly overhead if you are at the north pole?
Polaris
Which is TRUE about latitude by meridian passage position fixing method?
the position line that the latitude by meridian passage method will be parallel to the meridians of longitude
Which position is illustrated in the Figure?
Latitude from Polaris
Which point of celestial sphere is indicated by letter “B”?
nadir
Which position fixing method is illustrated in the Figure?
Sun-Run-Sun
What is the True Observed altitude of the sun?
81°08.6’
Who stated that when a body is acted upon by an external force, its acceleration if directly proportional to that force?
Isaac Newton
Which publication contains such information?
Nautical almanac
Why are Mercury & Venus considered as inferior planets?
The orbits of Mercury & Venus are closer to the sun than the Earth’s orbit
Which letter represents to Sidereal Hour Angle?
B
Which error affects the part indicated by letter “E”?
Index error
Which system of coordinates are star charts based upon?
Celestial equator system
How much is the earth’s obliquity of the ecliptic relative to its orbital plane??
23°26’
Which celestial body are you calculating if
you are using this table?
star
Calculate the intercept of the body using the following data
0°19.9’ Away
Calculate the intercept of the body using the following data:
0°09’ Towards
What is the True Observed altitude of the sun?
80°55.6’
What is the angular distance from A to a point on the celestial sphere and is measured along a vertical circle from 0° through 180°?
Azimuth
Which chart projects the Northern stars?
C
Which position is Venus plotted from?
AP3
How do you acquire the index error?
By looking obliquely into the horizon mirror so you can see the graduated arc & its reflection, then adjust the micrometer drum where the line points at 0°
How much is the dip correction based on the Table?
2.8
What does arc GM indicate?
Longitude-West
Which group of planets is commonly used in navigation?
Venus, Mars, Jupiter, Saturn
Which is NOT an advantage of using longitude by meridian passage in position fixing?
Uses single line of position
Which body is plotted from AP3?
Venus
Which celestial body are you calculating if you are using this table?
Sun
What is the advantage of this method of position fixing?
relies on accurate measurement of course & distance travelled to calculate the transfer
Calculate the intercept of the body using the following data:
37°56.8’
Which star or planet is plotted from AP2?
Capella
What is known as the hour circle through the vernal equinox?
First point of Aries
What is your latitude?
31°53.6’
What is your latitude if you are sailing in the northern hemisphere, same as the sun’s, with sextant angle taken during meridian passage of 42°06.7’ and the declination is 5°24.9’?
42°28.4’S
Which point is indicated by letter “E”?
Azimuth
Which formula of meridian passage is used to solve for latitude if you are in the opposite hemisphere of the sun?
(90° – Sextant Angle) – Declination of the sun
What is the correct term for letter ”D corresponding to other celestial coordinate system?
Declination
What is the correct term for letter ”C” corresponding to other celestial coordinate system?
Celestial Sphere
What is the Zn of Venus?
230° (Towards)
Which point of celestial sphere is indicated by letter “A”?
Nadir
Which part of the almanac gives the time for meridian passage based on the Figure?
D
What is the concept of the figure?
Illustrates relationship between various hour angles & meridian angles
Which publication contains all the tables required for coastal & deep sea navigation, a simple uniform method of interpolation for all the trigonometric tables, certain tables and data which are not readily available on board ship or are only used in the examination room?
Nautical Almanac
What is the advantage of this method of position fixing?
Plotting latitude on the chart without the need to measure any bearings
Which statement is NOT true about Keppler’s planetary law of motion?
The squares of the sidereal periods of any two planets are proportional to the cubes of their mean distances from the sun
What is the hour circle of the vernal equinox if measured from the observer?
PsΥ
When should this position fixing method be best taken?
Noon
In the horizon system of coordinates, which coordinate is similar to the meridians of longitude?
C
Which formula of meridian passage is used to solve for latitude if you are in the same hemisphere of the sun?
(90° – Sextant Angle) + Declination of the sun
What is the latitude of the fix position?
24°43’ N
Which is TRUE about inferior and superior planets?
Superior planets can pass behind the sun but cannot pass between the sun and the earth
What is the correct term for letter ”A” corresponding to other celestial coordinate system?
Ascension
Which star or planet is plotted from AP1?
Vega
Which publication consists three volumes of comprehensive tables of altitude and azimuth designed for the rapid reduction of astronomical sights in the air?
Sight Reduction Table
Which is NOT an advantage of the intercept method of position fixing?
Using a complete set of stars at a single point in time allows you to calculate a full position fix
What do letters A & B signify in the illustration?
Celestial coordinates
What does letter “C” stand for?
Greenwichhourangle
Which part measures the minute of a degree?
D
