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.
〔天文〕光学双星，视双星
Example sentencesExamples
The physical doubles (or binary stars) are much more numerous than the optical doubles.
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.
Definition of optical double in US English:
optical double
noun
Astronomy
Two stars that are in the same line of sight as seen from the earth, but that may be at far different distances.
〔天文〕光学双星，视双星
See also double star
Example sentencesExamples
The physical doubles (or binary stars) are much more numerous than the optical doubles.
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.