CASSENS & PLATH BOBBY SCHENK Sextant Handhabung Seite 19

Instructions
BOBBY SCHENK Sextant
_______________________________________________________________ Page 4
Application
The sextant is used for astronomical position finding at sea.
In coastal waters horizontal angle measurements can be carried out for terrestial navigation.
With a sextant the navigator measures the vertical angle between the visible horizon and a
celestial body. From this apparent angle one can calculate the true star height as required for
astronav calculations by applying various corrections to be found in the nautical almanach.
At the time of star observation the Greenwich time (world time or UTC) has to be determined. Star
altitude, UTC and the dead reckoning position allow calculating a line of position (LOP). The
intersection of two LOPs gives the true position or FIX.
Technical Data
Angle range ..................................................................................................... -5° ... +125°
Instrument errors ................................................................................................... < +/- 5"
Reading accuracy ........................................................................................... 10" or 0.17`
Weight....................................................................................................................... 1.8 kg
Batteries type AA or R6 (1.5 V) ........................................................................................ 2
Horizon Mirror ........................................................................................................ full view
Dimensions of index mirror .............................................................................. 56 x 42 mm
Dimensions of horizon mirror ...............................................................................  56 mm
Material of storage box .............................................................................................. wood
Frame material ............................................................................. seawater resistant brass
Material of mirror frames ....................................... seawater resistant Magnesium Al alloy
4 x 40 Telescope:
Principle ........................................................................................... Galilei, upright picture
Magnification ................................................................................................................. 4 x
Objective diameter ................................................................................................... 40 mm
Aperture .......................................................................................................................... 8°
Field of view ................................................................................................. 131 m/1000 m
Exit pupil .................................................................................................................... 5 mm
Luminosity, geometric ................................................................................................... 100
Twilight factor ............................................................................................................... 12.7
Focussing ............................................................................................. rotatable eyepiece