Even today, the celestial co-ordinates we use are based on references to the positions of extra-galactic radio sources. See for example ICRF (1) (1) https://en

Even today, the celestial co-ordinates we use are based on references to the positions of extra-galactic radio sources. See for example ICRF (1) (1) https://en.wikipedia.org/wiki/International_Celestial_Reference_Frame https://en.wikipedia.org/wiki/International_Celestial_Refere...