The marine sextant is a kind of reflection type angular measuring optical instrument. 
Application: 
Measuring the altitude of celestial bodies to determine the position of the ship at sea. 
Measuring the two horizontal angles between three known position land objects the ship location on chart by the help of a station pointer. 
Measuring the vertical angle of a known altitude objection to obtain its distance. 
Technical Data: 
Type: GLH130-40 / GLH130-60 
Measuring range: -15° to 130°/ -15° to 130° 
Accuracy(peak to peak value): 40'' / 60'' 
Readability: 12''  
Temperature range: -30°C~+50°C / -30°C~+50°C 
Telescope: 3.5×40 / 3.5×40 
Lamp voltage: 3V  
Net weight: 1.2kg