naked eye

bare eye, unaided eye (not aided by artificial visual devices)

The naked eye is a figure of speech referring to human visual perception that is unaided by enhancing equipment, such as a telescope or binoculars. (It, therefore, does not refer to smaller scale aids such as glasses.) The term is often used in astronomy when referring to events that can be viewed by the general public, such as astronomical conjunctions, passage of comets or meteor showers. Sky lore and various tests demonstrate an impressive wealth of phenomena that can be seen with the unaided eye.
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Noun
1. the eye unaided by any optical instrument that alters the power of vision or alters the apparent size or distance of objects; "it is not safe to look directly at the sun with the naked eye"
(hypernym) eye, oculus, optic

(See the naked eye)

Synonyms and related words:
baby blues, banjo eyes, bright eyes, clear eyes, command, cornea, domination, eye, eyeball, eyelid, eyereach, eyeshot, eyesight, field of view, field of vision, goggle eyes, horizon, iris, ken, lens, lid, limit of vision, line of sight, nictitating membrane, oculus, optic, optic nerve, orb, organ of vision, outlook, outlook over, peeper, perspective, popeyes, prospect, pupil, range, retina, saucer eyes, scan, sclera, scope, scope of vision, sight, sightliness, starry orbs, survey, unaided eye, view, vista, visual organ