And like constellations, those clusters are only observable together from a particular vantage-point (the earth), as soon as you go elsewhere (e.g. Alpha Centau

And like constellations, those clusters are only observable together from a particular vantage-point (the earth), as soon as you go elsewhere (e.g. Alpha Centauri) the stars are in a totally different place and the constellations, as originally defined, simply don't exist.