Author Archives: Ken Gebhart, Jr.

NASA Selects Astra III Professional for testing on ISS.

Sextants have been used by sailors for centuries, and NASA’s Sextant Navigation for Exploration Missions (Sextant Navigation) investigation takes the Celestaire Astra III Professional Marine Sextant to Space. In this clip is the Celestaire Astra III Professional Marine Sextant modified with 7×35 Prism Telescope. The Sextant Navigation for Exploration Missions (Sextant Navigation) investigation focuses on stability and star sighting opportunities in microgravity. Astronauts […]

Image Stabilizing (IS) Binoculars

Many people say that buying image stabilizing (IS) binoculars ranks among the top 3 most important things they have ever bought for their boats. You will see buoys, radar contacts, and navigational hazards much farther away than with non-stabilized models. How much stabilization is needed? When binocular power increases above 8, hand tremor and platform [...]

About Chinese Sextant Knockoffs

The Astra IIIB has been made for us in China since 1986 and it is produced in accordance with our specific quality guidelines. It has somewhat revolutionized celestial navigation because never before has such a high quality, accurate metal sextant been available at such a low price. Over 26,000 sextants of this model have been [...]

Why Celestial Navigation

FOR ELECTRONIC BACK-UP GPS is wonderful. World-wide coverage and reasonably priced receivers (both installed and handheld) contribute to maritime safety through accurate positioning of vessels. Yet, some back-up is needed. Instances of electronic failure, total electric failure, lightning strike, and flooding are often documented. Even battery powered handhelds can be rendered inoperable in these ways. […]

How Does Celestial Navigation Work

1. Imagine that the sun is directly overhead at a particular time. Then we simply look into the Nautical Almanac to find out where the sun is; and that is where we are! 2. How do we know the sun is directly overhead? The sextant tells us. It measures the angle from the horizon (meaning [...]

Using a Sextant

A sextant is an instrument generally used to measure the altitude of a celestial object above the horizon. Making this measurement is known as sighting the object, shooting the object, or taking a sight. The angle, and the time when it was measured, can be used to calculate a position line on a nautical or aeronautical chart. [...]