Astra IIIB Sextant Split View

Construction Details The frame is made from lightweight aluminum alloy which resists corrosion.

Aluminum alloy is not new to sextant construction. It has long been used by many manufacturers for lightweight versions of their heavier brass or bronze sextants in order to reduce arm fatigue and unsteadiness among infrequent users.

The sextant is electrically lighted by an LED on the arc and drum. The Astra IIIB is considered by many to be the easiest sextant to use. Its light weight and excellent balance makes it a pleasure to hold and makes sights easier to take under dynamic weather and sea conditions. Even reading the sextant is easier under low light conditions by having white degree marks against a black background as opposed to scribe marks on a brass arc. The index mirror is rectangular in shape and is the same size as used more expensive sextants.

This shape allows more aspect of the mirror to be available for high angle sights. This means the sextant does not have to be held as steady for them. An index mirror upgrade kit is available for older models having smaller, round, index mirrors. It comes mounted in a rectangular frame and has instructions for easy installation. We are impressed with the degree to which each component of the sextant is tested. For example, each mirror and shade glass is tested for perfect flatness by the Fresnel diffraction pattern method.

The sextants are assembled and tested in a clean, professional, environment. Random units have been tested by us and several professional navigators, with results that rival the most expensive German and Japanese models. Features The ability to quickly and economically change the type of horizon mirror is an attraction of this sextant to many navigators. This is because whole horizon mirrors are generally preferred by beginners who later may wish to change to a traditional mirror as proficiency is attained.