Abrams SC-1, Техническое руководство

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OPERATION
shadow bar which has
been
properly
set.
It
is
impossible to
make foresights
because
reference points are
difficult
to observe
and maintain.
(4)
Using
the
Sun Compass at Night.
(a)
The sun
compass
may also
be used
at night by deter
mining north
from Polaris (north star). Figure
8
shows
Polaris,
the constellation "The
Little Dipper"
(Latin
name
—
Ursa
Minor, of
which
Polaris is
the
end
star in
the handle
of
the
dipper),
and two other constellations, the Great
Dipper
(Latin
name
—
Ursa
Major)
and Cassiopeia.
Ursa Major
is
called the
Great
Dipper
because
of
the outline formed
by
its
seven
bright
stars.
A
pair
of
these
on
the
side
of
the bowl opposite the
handle are called
the
"pointers"
because a
line
connecting them,
points at
Polaris. Polaris
lies about
halfway
between the
constellations
Ursa Major
and Cassiopeia.
All
of
these
stars
shown
in
figure
8
are easily recognized
during
any clear night
by
an observer north
of
the tropics.
(b) Orienting
the Vehicle
to a
Predetermined
Azimuth.
(1) Screw the three-inch
radium
tipped sighting rod into the
hole provided
in
the date bar.
(2)
Loosen the clamping nut and
turn
the date bar to the
degree
mark
on the
protractor
which represents the predeter
mined azimuth.
(5)
Turn
the
vehicle
until Polaris is
aligned
with
the short
sighting rod and the gnomon rod.
The
vehicle
is
now
headed
on
the
right
course.
(c) Determining Unknown
Azimuths.
(1)
Turn
the date bar
until
the luminous
tips of
the sighting
rod and the gnomon rod are in alignment
with Polaris. The
arrow
on the date bar is now
pointing
approximately true north.
(2)
The
unknown azimuth
in
which the vehicle
is
headed
is
taken
from
the protractor. The
arrow
on the date
bar
points to the degree mark which represents the azimuth.
(d)
Using Stars
as
Foresights.
Stars
near the horizon
may
be used
as foresights.
However,
these
stars
move
and the azimuth should
be checked
by
Polaris
at
intervals
of
15
minutes.
10