The quality of the Tamaya Spica Sextant has been proven in many years of use by ocean-going navigators. Interchangeable telescopes are available in 4x40mm or 7x35mm. It features a special eye protector and full illumination of both the arc and drum. The measuring range is -5 degrees to 125 degrees. The accuracy is plus minus 10 seconds. The 4 x 40mm telescope has a 7 degree angle of view and the relative brightness is 100. The 7x35mm telescope has 6.5 degree angle of view and the relative brightness is 25. The frame is lightweight die cast aluminum alloy with corrosion resistant black finish. The index mirror is 57x42mm and it is aluminized on the rear side. The horizon mirror is 57mm diameter. There are 4 shades for the index mirror, 3 for the horizon mirror and one special shade glass and one Polaroid glass for the eyepiece of the telescope. It weighs 4 lbs. and it''s carrying case is molded plastic with two slide locks. The telescopes for this sextant are sold separately.