Eight-inch Drum Solid Brass Nautical Sextant By Nauticalmart The sextant weighs 5 lbs, measures 11.5" tall, 10.5" wide, & is 5" deep. A micrometer drum is used to change & read the azimuth angle. The telescope produces a bright clear image, & can be extended to focus & collapsed for storage. When the sextant is set to zero degrees, the image through both optical paths as viewed through the telescope align to produce a single image. When viewing two objects, such as the horizon & a celestial body, the index arm is adjusted until the two are superimposed. The micrometer drum reads out the angle between the two objects.