Sextant Astra IIIB - Traditional Splitview
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  • Sextant Astra IIIB - Traditional Splitview
  • Sextant Astra IIIB - Traditional Splitview

Sextant Astra IIIB - Traditional Splitview

Weems & Plath
Fabriqué aux USA
Sextant Astra IIIB - Traditional Splitview

Data sheet

Fabriqué aux USA
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Description détaillée

The Astra IIIB has somewhat revolutionized celestial navigation. Never before has such a precise and quality metal sextant been available at such a low price. More than 24,000'sextants of this model have been sold in the United States alone in the last 27 years; much more than any other serious sextant. Its popularity has spread to the rest of the world, making it the most recognized (and most supported) sextant in the world.

Its low price, excellent optics and choice of horizon mirrors and other accessories make it the perfect choice for beginners. Yet, we know several professional browsers who prefer the ASTRA IIIB simply because they can leave their expensive models at home without sacrificing significant accuracy. The Astra IIIB is manufactured by Changzhou Celestaire Instrument Co. in China, with which Celestaire is a joint venture, and it is produced according to our specific quality guidelines.

Construction Details

The frame is made of lightweight aluminum alloy that resists corrosion. Aluminum alloy is not new for sextant construction. It has long been used by many manufacturers for light versions of their heavier brass or bronze sextants to reduce arm fatigue and instability in casual users. The sextant is electrically lit by an LED on the bow and the drum.

The Astra IIIB is considered by many to be the easiest sextant to use. Its light weight and excellent balance make it a pleasure to hold and make the sites easier to take in dynamic weather and sea conditions. Even reading the sextant is easier in low light conditions by having white marks on a black background as opposed to scribe marks on a brass bow.

The index mirror is rectangular in shape and the same size as the more expensive sextants. This shape makes it possible to have more aspect of the mirror available for the high-angle views. This means that the sextant does not need to be kept as stable for them. An index mirror upgrade kit is available for older models with smaller, round index mirrors. It comes mounted in a rectangular frame and has instructions for easy installation.

We are impressed by the extent to which each component of the sextant is tested. For example, each mirror and shading glass is tested for perfect flatness by the Fresnel diffraction method. Sextants are assembled and tested in a clean and professional environment. Random units have been tested by us and several professional browsers, with results that rival the most expensive German and Japanese models.


The ability to quickly and economically change the type of horizon mirror is an attraction of this sextant for many browsers. Indeed, full horizon mirrors are usually preferred by beginners who may later wish to switch to a traditional mirror when the skill is reached.

The ease of maintenance is appreciated by schools and other groups who, because of their intensive use, need cheap spare parts because of the threat of student mishandling.

equipment included and optional

The sextant features bow and drum LED lighting powered by two standard size AA batteries (not included) that fit into the handle. It comes in a varnished wood case, with instruction book, certificate of accuracy, and adjustment key. The external dimensions of the case are 6.5 x 13 x 11 inches. It includes a 3.5 x 40 monocular telescope as standard equipment.

Optional accessories include a 7x35 prism telescope, a pull-on rubber eyecup for use with glasses and a zero-magnification sight tube. A bubble horizon of practice is available, which facilitates effective practice of the backyard without the need for a marine horizon. Although the sextant has the choice between an entire horizon or a traditional split-horizon mirror, an additional mirror of either type is available at nominal cost, and is already mounted in its frame. The mirrors are changed quickly with two easy-to-handle screws.


  • Arc: -5 ° + 130 °, radius 153 mm
  • Accuracy: ± 20 ", all along the arc
  • Micrometer Drum: 1 'scale, vernier to 0.1'
  • Horizon Mirror: 51 mm in diameter
  • Index mirrors: 56 x 42 mm
  • Blinds: 4 indexes - 3 horizons
  • Weight: 2 lb., 10 oz.