The first thing on the moon that could be visible from earth is already there.

[A mirror.][1]

> Will anyone notice, 100 feet away, something else Armstrong left
> behind? Ringed by footprints, sitting in the moondust, lies a 2-foot
> wide panel studded with 100 mirrors pointing at Earth: the "lunar
> laser ranging retroreflector array." Apollo 11 astronauts Buzz Aldrin
> and Neil Armstrong put it there on July 21, 1969, about an hour before
> the end of their final moonwalk. Thirty-five years later, it's the
> only Apollo science experiment still running.

Although it can not be viewed by binoculars, it can be seen by telescopes if one times it right.

But guaranteed, any large solar array would reflect light back to earth when the moon is in the correct position, and the flash would be easily seen by binoculars.

  [1]: https://science.nasa.gov/science-news/science-at-nasa/2004/21jul_llr/