Definition of optical double in English:

optical double

noun

Astronomy
  • A group of two stars which appear to constitute a double star due to their being in the same line of sight as seen from the earth, but are actually at different distances.

    • ‘At first he figured that such pairs consisted of two stars vastly distant from each other but coincidentally lying along a single line of sight - a visual phenomenon we now call optical doubles.’
    • ‘The physical doubles (or binary stars) are much more numerous than the optical doubles.’