As the search for quality previously owned sextants becomes harder, and harder,
I decided to investigate the ASTRA III B sextant, that I had only read about. It was conceived by Ken Gebhart of Celestaire,
and manufactured to his specifications in China. Ken is the oldest, in terms of length of time in the business, of those of
us who were selling sextants in its hey day. He an I knew each other from back in the mid 1970's, and strangely
both our companies were based in the Mid West. Since then, our wakes have crossed once or twice.
The manufacturer's literature states that the Astra IIIB has revolutionized
the metal sextant market by introducing a high quality, accurate, metal sextant at a low price. Over 13,000 sextants
of this model have been sold in the US alone in the past 15 years; far more than any other serious sextant. Its popularity
has spread throughout the rest of the world as well. It is easy to see why. The sextant has the looks and feel of a fine piece
of precision engineering and is detailed to a very high standard all around.
The frame is made from lightweight aluminum alloy which resists corrosion. Aluminum
alloy is not new to sextant construction. It is currently used by Tamaya, Freiberger and by C. Plath for a lightweight version
of their famous Navistar Classic sextant. The Astra sextant is electrically lighted by LED on the arc and drum. Batteries
NOT included. Its low price, excellent optics, and choice of horizon mirrors and other accessories makes it a good choice
for beginners and professionals.
Manufacturing: The Astra IIIB is made by the Changzhou Celestaire Instrument Co.
in China and is subject to stringent testing. 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.
The Astra IIIB is seen in two models: standard and deluxe. The difference is in the
index mirror. The Standard model has a round index mirror with the silvering applied to the rear surface of the glass.
It has less surface area, and is not as good for twilight use. This is the way all ASTRA IIIBs were before 1994. At that time
the Deluxe model was introduced with a rectangular index mirror having the silvering applied to the front surface (the mirror
is interchangeable in size with most other full size rectangular mirrored sextants). From an engineering standpoint, this
arrangement allows for a larger reflecting profile during high angle observations, and better reflection brightness for all
sights. Such improvements, are more easily noticed by the user doing twilight star and planet sights. From a practical standpoint,
the biggest improvement is in durability of the silvering itself. When applied to the front surface. it is easy to keep clean
and free of saltwater contamination. It is further protected by a durable oxide coating. In contrast, rear silvered mirrors
need resilvering more frequently if saltwater becomes trapped between the mirror and its housing and is not faithfully rinsed
out.
The horizon mirror for this unit is the whole horizon (WH) type) which is felt by
many to be easier to use and longer lived, and is a costly option on other sextants with which the Astra competes.
CREDENTIALS: For purposes of judging whether my opinion counts, I was the editor of the
chapter on sextants of the 1977 Edition of "Bowditch", The American Practical Navigator, NAVPUB 9; a member of the U.S.
Naval Academy Navigation Symposium Board, 1975-1978; the author of a book on marine sextants, Cornell Maritime Press,1975,
and the founding president of Nautech Maritime Corporation which partnered with Tamaya of Japan in the introduction of the
MS 733 Spica, the MS 833, Jupiter, MS 933 Venus sextants and the famous NC-2 navigation computer, in the U.S. market.
I am also a retired Master Mariner, and hold a U.S. Navy "D" Qualification as a Senior Skipper - Oceans.
Included and Optional Equipment:
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 varnished wooden case, with instruction book, certificate
of accuracy, vial of oil, and adjusting wrench. It includes a 3.5x40 monocular telescope as standard equipment.
NEW ASTRA III B DELUXE Sextant SPECIFICATIONS:
Complete with Manufacturer's ONE YEAR WARRANTY
Inspection Certificate reads: This instrument is free of error for practical use
- Guaranteed accuracy: 20" arc
- Measuring Range:-5 to +130 degrees
Telescope:
3.5 x 40mm: Coated optics
- Frame: Lightweight die cast aluminum alloy with corrosion resistant light gray finish.
- Micrometer Scale: reads to 1.0 min. Vernier to 2/10 min
- Index Mirror: 56 x 42 mm. aluminized on the front side.
- Horizon Mirror: 51mm diameter.
Shades:
- 4 for index mirror
- 3 for horizon mirror
- Sextant Weight: 2lbs, 10 oz. 10.0 lbs in case
- Carrying case: Hi Gloss Varnished Mahogany case with bronze clasps
SHIPPING &
PACKING: Due to the nature of this item, extra protective packaging is provided for shipment. The
cost of shipping, packing, handling, and insurance to your destination, is extra, and is a flat $25.00. We price
shipping honestly, but expect to be reimbursed for the nominal cost of packaging materials and handling.
