condition: new make / manufacturer: Celestaire Sextant model name / number: Astra III-B Sextant
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Celestaire Astra III-B Sextant with Whole Horizon Mirror
When it was first imported, the Astra IIIB somewhat revolutionized celestial navigation. Never before was such a high quality, accurate metal sextant available at such a favorable price. Over 26,000 sextants of this model have been sold in the US alone in the past 30 years; far more than any other serious sextant.
This light weight aluminum sextant is actually easier to use than more expensive 4-pound brass models. The optics are excellent and the instrument has an excellent ergonomic feel.
It is unlikely that any navigator regardless of experience could do more accurate navigation underway in a small vessel with any other sextant, even those costing $2,000 or more.
The index mirror is rectangular in shape, and has the silvering applied to the front, rather than the rear surface. This is similar to the way astronomical telescopes are silvered. From an engineering standpoint, the rectangular shape allows for a better reflecting profile during high angle observations, and the front surface silvering provides better reflection brightness for all sights.
From a practical standpoint, the biggest advantage is in the durability of the silvering itself. When applied to the front surface it is easy to keep clean and free of saltwater contamination and it is further protected by a durable oxide coating.
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.
The sextant has LED lighting of the arc and drum powered by two standard size AA batteries (not included) which install in the handle. It comes in a sturdy varnished wooden case, with instruction book, certificate of accuracy, and adjusting wrench.
Case external dimensions are 6.5 x 13 x 11 inches. Includes a 3.5 x 40 monocular telescope as standard equipment.
Comes with the Following
Wooden Carrying Case
Serial Number Available on Request
Arc -5° + 130°
Accuracy ± 20", throughout the arc
Micrometer Drum 1' scale, vernier to 0.1'
Horizon Mirror 51 mm diameter
Index Mirrors 56 x 42mm
Shades 4 index - 3 horizon
Sextant Weight 2 lbs., 10 oz
RETAIL COST: USD $659.00
CONDITION: NEW. Only used a few times for practice sights. Never exposed to salt air or salt water.