C. Plath, Hamburg Professional-Grade Premium |
the only professional-grade fully-functional, factory-callibrated sextant in commercial production today |
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Nine out of ten sextants being sold on ebays are decorative or sentimental crap so be careful when you invest in something that merely looks good or is promised as "uncallibrated but functional" (whatever that means!). On sale here is a professional-grade, factory callibrated C. Plath, Hamburg serialized sextant reproduction, each with a unique serial number, and with full printed instructions on how to use. It also comes with our guarantee of accuracy to within +/- 5% or even less compared to your GPS readings. If you want to buy merely a display sextant, we would not recommend this since it is designed for serious functionality (right from its low maintenance buffed finish) and extra large mirrors and filters and 8x telescope. This is one of the best contemporary brass sextants available in the market, in fact the only commercial-grade sextant in production today. These are made in very limited quantities given the dying demand for these beauties. Factory callibrated for professional-grade accuracy. Comes with instruction sheets that trace the historic significance of the sextant and also operational instructions and tips. A very high-quality teakwood carrying and display case weighing over 4 lbs is included in the sale. I have very few units of this model so whether you are a serious collector of classic sextants or own a store, this one is for you at our guaranteed unbeatable facotory prices.. |
A sextant is a very important mathematical instrument for navigating at sea. It can also be used in astronomy. It
is used to measure the angle between two far away objects. Most often these objects are the sun and the
horizon, or the pole star and the horizon. Sometimes the angle between the horizon and stars or the moon can
also be measured with a sextant. The original Ross London sextants (on which this replica unit is authentically based) were made in England at the end of the 18th century. The biggest problem for sailors in the 18th century was finding their position in the middle of the oceans during long journeys. Sailors needed to be able to find both their latitude (which was their position north or south on the earth) and their longitude (which was their position east or west on the earth). Sextants helped them to find out both of these things. Before the invention of satellites and electronic satellite navigation systems it was very hard for sailors to find their position at sea. Many shipwrecks occurred because captains got the positions of their ships wrong. This not only caused the deaths of many seamen but also had big political and economic implications for the government because lots of battles happened at sea or valuable cargo could be lost in shipwrecks. Sextants are made with a circular curve that is one sixth of a circle. The curve is divided up like a protractor. It is used for measuring angles so it is labelled with degrees. The other important parts of a sextant are a telescope, a piece of glass which is half see-through and half mirror (called the horizon glass), and a moving arm which has another mirror fixed to it. In earlier times, marine sextants had a fixed telescope leveled on the horizon and a radial arm is moved against an arc scaled in degrees. The radial arm is adjusted to get the reflection, of a known star, from index mirror and then off the horizon mirror down the telescope until it lines up with the horizon. The position of the radial arm on the scale gives the stars elevation. The nautical sextant range includes: slow motion nautical sextant, octants, slow motion nautical sextants and round dubble telescope nautical. In modern navigation sextants, the light ray from the celestial body is reflected in two mirrors (in series) one of which is adjustable and the other is half silvered. By rotating one mirror and its attached index bar, the image of the body is brought down to the horizon. The rotation measures the altitude on the limb. Using a Sextant Text available upon purchase Why Bigger is Better The size of the mirrors on a sextant generally vary directly with the quality of the instrument. Large index and horizon mirrors are desirable because larger mirrors admit more light, making it easier to obtain sights in marginal conditions. Larger mirrors also lessen the possibility of losing the image as the body is brought down to the horizon. The heavier weight of a brass sextant provides greater steadiness and hence more accurate readings, especially if it is windy. As the observer develops proficiency and speed in sight taking, fatigue becomes less of a factor. The 3.5 to 4 power magnification helps you find and maintain stars in view in both calm or pitching seaways. A 6x30 or 7x35 monocular of greater magnification is well suited for sun sights, or the greater heights of eye associated with large ships.The increased magnification allows the sun's diameter to appear larger, and better defines a more distant horizon. This helps the navigator determine the point of tangency of the sun's limb and the horizon. The increased magnification however makes finding and holding sights more difficult on a moving deck. A Sight Tube of zero magnification affords a wider field of view for rough weather, horizontal angles, and finding stars. If your sextant is to have only one scope, a 3.5x or 4x would be the logical choice for yacht sized vessels. Many sextants have an option of either the traditional (half-silvered) horizon mirror or what is called a "whole horizon mirror". With the traditional mirror, the horizon glass is divided vertically into two halves producing a "split image." The half nearest the frame is a silvered mirror and the other half is clear glass. In some cases this clear glass is eliminated. A later development in sextant technology is the whole horizon mirror. Using specially coated optics, the whole horizon mirror superimposes both the horizon and the celestial body on the entire mirror with no split image. This greatly simplifies "bringing down" the celestial body and makes it easier to hold the body in view. A draw back to this system is a very slight reduction in light transmission and reflection which may affect marginally lighted observations. Some feel these two aspects are a trade off; that is, one can more quickly take observations with the whole horizon mirror, and be finished before marginal conditions occur. In general, professional navigators tend to favor the traditional horizon mirror while beginners tend to favor the whole horizon mirror. |
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