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The 187-S was specifically designed for quick, precise leveling of alignment telescopes and collimators.  It can also be used to level any cylindrical surface between 1¾" and 3" in diameter.  Like many of our levels, both ends of the bubble are viewed simultaneously by using prisms and a magnification system.  This "coincidence" or "split" bubble presentation ensures the most accurate reading of the position of the bubble (see sketch below).  The bubble is conveniently viewed from any position via the 360-degree rotating turret assembly on top of the unit.  The 187-S will indicate off-level conditions as small as one arcsecond.  An elastic strap is included to secure the level to the instrument.  The coincidence vial is supported by two hardened, ground, inverted "Vs" on a 5" center.

Have a look at the various other level vials for use on our optical tooling instruments or for general purposes. The 187-S is classified as National Stock Number (NSN) 6650-D50-0065.