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.