Colour Period Diagrams in the Era of Gaia DR2

The rotational evolution of main sequence stars is still not fully understood for specific masses and ages. Also the influence of additional parameters like e.g. metallicity have to be investigated more carefully. In order to gain a better understanding, we need to probe stellar open clusters in different age regimes to improve our models. I present two open clusters (NGC6633, IC4756) whose stellar memberships vastly improved with the advent of Gaia DR2. The rotation periods have been determined with Lomb Scargle and Clean respectively and refined using phase dispersion minimization. Using astrometric membership helps to clean up the colour magnitude diagrams. Gaia DR2 colours prove to be more reliable than most ground based surveys