Russian-made sextant of World War II made of gray painted metal complete with original wooden box with accessories. Good condition. Size in CM 26 x 18 x 8 In order to measure a height of a star (for example, the Sun), you have to set the instrument in a vertical plane and, looking through the sight device, to mark out the line of the horizon visible through the non-silvered half of the fixed mirror. Moving the alidade that is together with this mirror, make sure that the light rays coming from the star, and then reflected by the mobile mirror and by the silver half of the fixed mirror, be directed from the fixed mirror to the observer: if you look through the sight device, you see the image of the star, obtained for double reflection, coinciding with the line of the horizon. The height of the star is expressed by the angle whose value is read on the graduated scale. The filter is used when the star is the Sun.