You are in the middle of nowhere, there is no signal and
even your phones GPS is not catching on. You know that there should be a river
to the east, and following it will bring you back to civilization. But where is
east? You have heard of people using the North Star or Polaris to navigate, as
it always points to the north. But how do you find the Polaris and after that
Polaris is the only star in the sky that is almost
completely stationary, always found in the same spot on the sky regardless of
the time of day, and this while all other stars move around throughout the
night. This is because of the simple fact that it happens to be on the extended
rotational axis of the Earth. Everything rotates around this axis, and the only
reason that it looks different is because you are probably not on the North
Pole, where all stars move in a circle above your head, with Polaris in the
dead center. There is nothing special about Polaris other than that it happens
to be in this location right now, which is convenient for us. But in a few tens
of thousands of years, it will have moved out of this spot, leaving no easily
identifiable ‘north star’, much like is the case on the southern hemisphere
currently. Fortunately, Polaris is here to stay for now, and we can use it for
navigation, by using the following methods.
## Help from the constellations
The easiest and quickest way to find Polaris during a
cloudless night is to use other constellations as a point of reference. You
will need an unobscured and cloudless sky for this or at least a sky that is
clear enough to see the stars. The easiest constellation to see is the big
dipper, which consists of the bright stars of the Ursa Major constellation.
This well-known constellation is easily found by most, even in bright cities
with strong light pollution. Once it has been identified, all one needs to do
to find Polaris, is to extend a line from the outer two most stars, about five
times the distance of the two initial stars. The closest bright star in that
vicinity is Polaris. Alternatively, one can look for the constellation
Cassiopeia, which is also very bright in the sky in the form of a bright ‘W’.
(Or M depending on your location and time.) The middle rung of the ‘W’ can be extended
in a similar way until one comes to the brightest star along that line. Of
course, seeing both Cassiopeia and the big dipper makes it even easier to find
Polaris. The relative height on the sky of these constellations varies with
latitude, where Polaris will be right above your head on the North Pole and right
on the horizon at the equator. The further south you go, the harder this method
becomes to use properly, as at some point Polaris is always below the horizon.
One might however still be able to see (part of) Cassiopeia or the Big Dipper
and get a rough estimate from there.
### The reference method
If you have trouble finding either of these constellations
due to partial overcast or thick foliage above you, it is still possible to
find north as long as some star is visible for a prolonged time. All you need
for this to work is two reference points, usually in the form of sticks or
rocks and a bit of patience. All you need to do is to place the two reference
objects in a line and align one eye with the star and the two objects. Now try
to keep an eye on the star without moving your head and see in which direction
it is moving. This effect is more accurately measurable the longer you wait, so
don’t rush it.
If the star moved up, you are looking east. While you are facing
west when it moves down, north when it moves left and south when it goes right.
If it moves on a diagonal, then you are in between two cardinal directions. In
our example, where the star moves down and right roughly equally, meaning that
we are facing the south-west direction. You can now guess true north or adjust
your reference points and try again to see if it moves mores as is expected.
This method works better the further away you are from
Polaris, again due to the fact that everything moved around that point and
further out stars move faster. In Europe and the US, it would be best to use
stars close to the horizon, and near the equator one would choose a star higher
up. This method can also be applied while exploring the southern hemisphere,
but remember to switch around all directions. So up is west, down is east, left
is south and right is north.
### Using your phone
The final method is a more advanced one, but still very
usable even in areas completely devoid of signals. All you need here is a smartphone
and a star finding an app like Stellarium (paid) or Google Sky (free). These apps
use the built-in accelerators and magnetometers to calculate the orientation
of your phone and use that to display the current night sky as is on any point
that you are pointing to. This allows you to easily find Polaris to orient
yourself. After this, the phone can be switched off to preserve battery for
later use, something that would not be possible if you choose to rely on a
compass app for example. The only drawback here is that the app uses the
longitude and latitude from the last time that it had a connection. This is
generally accurate enough but probably won’t work if you crashed halfway
between an intercontinental flight.
It is also worth mentioning that some phone covers have
magnets in them that throw off the on-board sensors. So be sure to test this
app before deciding to reply on it for purposes like this!
Written by Alex Pietrow
Editors Note - From the Desk of Bram
Alex Pietrow holds a Doctorate in Astronomy from Stockholm University, Stockholm, Sweden. This man is cross between McGuyver and Indiana Jones. When he is not looking to the sky, he is inventing new uses for technology or exploring untouched ancient ruins.
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