The presence of thorium can sometimes, depending on the mixture of other elements in the lens, cause moderate to severe browning of the lens elements.
Radioactivity in lanthanum containing lenses is due to the intentional inclusion of thorium in the optical glass mix. Despite statements to the contrary, lenses containing lanthanum are not appreciably radioactive - lanthanum is only 1/10,000th as radioactive as thorium. Like fluorite, its optical properties of high refractivity and low dispersion allows lens designers to minimize chromatic aberration and use lenses of lower curvature, which are less expensive to produce. Thorium oxide has a crystalline structural similar to calcium fluoride ( fluorite). Main source of radioactivity is the use of thorium oxide (up to 30% by weight) as a component of the glass used in the lens elements. There are a significant number of lenses produced from the 1940s through the 1970s that are measurably radioactive.
5.3 Lenses Tested non-Radioactive (by contributors to this page).5.2 Lenses Tested Radioactive (elsewhere, or by contributors to this page).5.1 Lenses Tested Radioactive (by the creator of this page).4 Lenses with elements made of radioisotope-containing glass.Shipping costs are for mainland destinations only.įor any other locations, please contact me for costs. International carrier please request a price. Please see photographs which form part of the description.
There are a few minor signs of use to the exterior of the case. The binoculars have a little paint loss to the exterior. The objective and eyepiece lenses are in very good condition with no scratches. The optics are good, clear and free from scratches.
This model has a 10-x magnification with 50mm lens.
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