The Cassens & Plath sextants are the most popular of the traditional solid brass professional sextants in the world today. Made in the finest tradition of German craftsmanship, it has a reported accuracy of better than 10 seconds of arc. The frame and arc are constructed of a special brass alloy, and the entire instrument has been treated and enameled to prevent corrosion. The handle is inclined to provide a more natural grip. The mirrors are of the finest optical quality. For daytime observations, sunshades are provided for both the index and horizon mirrors. Lighting of the micrometer drum and arc is powered by 2 size AA batteries contained in the handle. All models are supplied in a nicely finished wooden instrument case.
The Cassens & Plath is available in two models: the Standard, and the Horizon Ultra models. These two models are essentially identical, except that the Horizon Ultra incorporates a double prism lens which indicates perpendicularity of the sextant to the horizon.
In light of the foregoing if you want a traditional split mirror, the standard model is a good choice since the double prism lens feature of the Horizon Ultra could not be used anyway. Conversely, if you want a whole horizon mirror, the Horizon Ultra with the double prism lens is recommended.
Included and Optional Equipment
The sextant comes with a 3.5 x 40 telescope and wooden case as standard equipment. Optional accessories include a 7×35 prism telescope, a Slip-on rubber eyecup for use while wearing glasses, and a Zero-magnification sight tube. A Practice bubble horizon and a Professional bubble horizon are available which facilitates effective practice without the need for a sea horizon.