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Navigation by the North Star
In the Age of
Exploration, the open
ocean was a dangerous
place for mariners.
Good navigation was
vital for survival.
The North Star was
important for getting
around.
How to Find the North Star
You can find the North
Star by locating the
two bowl stars of the
Big Dipper.
Follow those stars in a
straight line to the first
bright star you see.
That is Polaris.
Cassiopeia and the North Star
You can also use
Cassiopeia to find the
North Star.
The North Star makes
an arrow with the
right-hand arch of
Cassiopeia.
Stars Motion Across the Sky
Stars move across the
night sky in circular
arcs.
This apparent motion
is caused by the earth
spinning on its axis.
The North Star is at
the center of the spin
so it does not appear
to move.
A Star Swirl on Film
Here is a photo of the
night sky with the
shutter left open. The
stars appear to move
in circular arcs. The
North Star is the star
in the center.
The Importance of the North Star
The position of the North Star is fixed
throughout the night.
And so, the angle of elevation of the North
Star remains constant throughout the night.
Therefore you can use the North Star to do
two things: tell you where north is and tell
you your latitude.
How the North Star is Viewed
from Earth
The North Star’s
position in the sky
changes as you move
from the North Pole to
the Equator.
It moves from being
directly overhead to
sinking down to the
horizon.
The North Star: At the North Pole
At the North Pole, the
North Star is directly
overhead.
The North Star: At the Equator
At the equator, the
North Star is at the
horizon.
Finding Your Latitude
If you measure the
angle of elevation of
the North Star, you
can determine your
latitude on the map.
Angle of Elevation =
Latitude on the Map
The Sextant
The sextant was a tool
that mariners used to
measure the angle of
elevation of stars and
the sun.
A Fisherman Using A Sextant
Here is a fisherman
measuring the angle of
elevation of the sun using a
sextant.
Sextants were used up until
the 20th century