Crossword-Solution: DIOPTER 7 letters, 7 clues 🏆 scrabble score: 10

Direct the index or diopter to the sun at noon, so that the same ray of light may shine through both holes in the two tablets or pinules on the diopter, and the diopter will point to the degree of the sun's meridian altitude indicated on the outer rim of the astrolabe.

The diffusion waves in this case emanate from the principal focus of the diopter, and therefore become plane on passing through the convex surface of the denser gelatine.

Also, if so great a degree of astigmatism is really the rule as is emphasized especially by Hirschberg[43] and Berlin,[44] then the simple refractive index usually given--sometimes within a half diopter--would be meaningless.

Among other early instruments were the astrolabe, an invention attributed to Hipparchus, which served mariners and others down to the seventeenth century; the diopter, which appears to have resembled an alidade mounted on a stand, and may be regarded as a prototype of the theodolite; and Ptolemy’s rods, or the triquetum, in which a rod working upon two others, one vertical while the other pointed to the observed object, enabled the angular zenith distance to be read.

USE OF THE SKI-OPTOMETER IN SUBJECTIVE TESTING In subjective refraction, especially where the “better or worse” query must be decided by the patient, it is commonly understood that the refractionist is compelled to first increase and then decrease a quarter of a diopter before the final lens is decided.