We present the fiducial sequences of a sample of Galactic star clusters in the five bands of the Pan-STARRS1 ( PS1 ) photometric system ( g _ { P 1 } , r _ { P 1 } , i _ { P 1 } , z _ { P 1 } , and y _ { P 1 } ) .
These empirical sequences – which include the red giant and sub-giant branches , the main sequence , and the horizontal branch – were defined from deep colour-magnitude diagrams reaching below the oldest main-sequence turn-offs of 13 globular and 3 old open clusters covering a wide range of metallicities ( -2.4 \la [ Fe / H ] \la + 0.4 ) .
We find excellent agreement for the nine clusters in common with previous studies in similar photometric systems when transformed to the PS1 system .
Because the photometric and spectroscopic properties of these stellar populations are accurately known , the fiducials provide a solid basis for the interpretation of observations in the PS1 system , as well as valuable constraints to improve the empirical colour– T _ { eff } relations .