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Astra IIIB Astra IIIB

The Astra IIIB revolutionizes celestial navigation:  never before has such a high-quality, accurate metal sextant been available at such a low price.  Tests by professional navigators produce results that rival those of the most expensive German and Japanese models.  

The Astra's frame is manufactured in China from a lightweight, corrosion-resistant aluminum alloy.  Mirror and shade glass are extensively machined and tested for perfect flatness.  Sextants are assembled in a professional clean-room environment. 

The Astra IIIB is available in two configurations:  the Deluxe and the Professional.  The Deluxe uses a rectangular index mirror that is silvered on the front surface.  This arrangement allows for simple replacement (size is compatible with most other sextant mirrors), better reflection brightness, and increased durability (it's much easier to keep clean and corrosion-free).  The Professional offers the highest precision with a bronze arc fused to the aluminum frame--the best of both worlds:  lightweight handling and high accuracy (+/-15").  It's the perfect choice for the discriminating buyer.

Both the Deluxe and Professional models are available with a whole horizon or traditional half-silvered horizon mirror.  Customers prefer the traditional mirror for the most precise star sights; some navigators feel that a whole horizon mirror simplifies sun and moon sights.  Replacement mirrors are available and are user-serviceable.  

Astra III B Deluxe Specifications


-5o + 130o, radius 153 mm
Accuracy 20 seconds, throughout the arc
Micrometer Drum 1' scale, vernier to 0.2'
Horizon Mirror 51mm diameter
Index Mirrors 51mm (Standard Model)
56 X 42 mm (Deluxe Model)
Shades 4 index, 3 horizon
Weight 2 lbs., 10 oz.

All Astra IIIB models include:

  • 3.5 X 40 monocular telescope

  • LED lighting of the arc and drum (requires two AA batteries, not included)

  • Varnished wooden case

  • Instruction book

  • Certificate of accuracy

  • Oil

  • Adjusting wrench

Telescopes, eyecups, practice horizons, and other accessories are also available.

Ordering Information
104638 Astra IIIB Sextant--Deluxe Model
Select Traditional Half-Horizon or Whole Horizon Mirror

whole horizon
half horizon
127982 Astra IIIB Sextant--Professional Model
Select Traditional Half-Horizon or Whole Horizon Mirror

whole horizon
half horizon
104661 Astra Whole Horizon Mirror in Frame $74.95
104660 Astra Traditional Half-Horizon Mirror in Frame $74.95
104659 Astra Slip-On Rubber Eyecup
For navigators who wear glasses
104666 Zero Magnification Sight Tube
For taking horizontal angles where magnification is not needed and where a wider field of view is helpful for identifying objects relative to one another.  Also useful in rough weather where a wider field of view is helpful in holding an object in sight despite sextant movement.
104647 Practice Bubble Horizon
For practicing taking sights without a natural (sea) horizon.  Use in place of the standard telescope.
200144 Davis Artificial Horizon
Fill the body with water to provide a reflecting surface for sextant practice.
104658 Sextant Calibrating Cylinders
Precisely-machined cylinders are used to remove the error of perpendicularity of the index mirror. 



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Contact for information.
(800) 584-4114 - (510) 769-1547