What further observation, also requiring the telescope, was needed to cement the proof for the heliocentric model?

Answer

Observations of the phases of Venus

The discovery of Jupiter’s moons was a major crack, but further work, including observations of the phases of Venus facilitated by the telescope, was required to finalize the proof of heliocentrism.

What further observation, also requiring the telescope, was needed to cement the proof for the heliocentric model?
Galileoastronomyobservationsheliocentric modelJupiter's moons