index prism

index prism

[′in‚deks ‚priz·əm]
(navigation)
A sextant prism which can be rotated to any angle corresponding to altitudes between established limits; the bubble or pendulum sextant counterpart of the index mirror of a marine sextant.
References in periodicals archive ?
All LX L models come with fully multicoated lenses and phase-corrected, high index prism glass.
Utilizing Nikon's multilayer-coated lenses and Bak4 High Index Prisms, these binoculars offer excellent image brightness and clarity.
1 mm of eye relief at 7x, a field view of 288 feet at 1,000 yards and a close focus distance of 26 feet, along with a 7-15 power zoom range, multicoated precision lanses and high index prisms.