Design - CASSENS & PLATH POLARIS Handhabung

Instructions
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Design

Index shade
glasses
Star elongation
lense
Horizon mirror
Shade glass
Limbus, arc
Drum with
minute scale
Red knob
At its lower end the sextant frame carries the arc or limbus with a graduation from -5° to +125°. An
angle of more that 90° can be used to check an unusual horizon dip. The alidade or index arm is
pivoted to the frame by means of a specially designed bearing that grants a minimum of slack.
Attached to the upper end of the index arm is the index mirror. The lower end of the index arm
supports the graduated drum with knurled knob and tangent screw, the vernier, the lever and the
index mark to read off full degrees. The drum has scale units of 1`. Decimal minutes may be read
from a vernier scale.
The telescope is detachable, and is fixed by a knurled screw to the body of the sextant.
The eyepiece is rotatable for focussing. The 4 x 40 mm optical system grants sufficient brightness
for twilight observations as well as enough magnification for coastal horizontal angle
measurements.
The horizon mirror is mounted in front of the telescope. In front of this a set of 3 differently tinted
horizon glasses (circular) is installed to dim the sun´s reflection on the water surface. A set of 4
differently tinted index shade glasses (rectangular) is located between horizon and index mirror.
These shade glasses are for light dimming of the doubly reflected celestial body (sun). In order to
ensure equal brightness of both images -especially during sun observation- the tinted glasses are
all of systematically graduated transparency and can be moved into the path of light singly or in
any required combination from either set of filters. All shade glasses stop transmission of non
visible light so that no harmful effects will be caused when looking into the sun through these
shade glasses.
The reverse side of the frame carries the handle with batteries for illumination and the legs.
The clear-view horizon mirror allows free horizon sight in the side areas. This simplfies the horizon
observation under poor brightness conditions. The reflection/transmission ratio in the middle half
silvered area is adapted to the human eye and makes it possible to keep the advantages of the
fullview mirror.
POLARIS Sextant
Index mirror
Mirror adjustment
screw
Telescope
Telescope
focussing
Sextant frame
Alidade, Index
arm
Lever