We present a deep Blanco/DECam colour-magnitude diagram ( CMD ) for the large but very diffuse Milky Way satellite dwarf galaxy Crater II .
The CMD shows only old stars with a clearly bifurcated subgiant branch ( SGB ) that feeds a narrow red giant branch .
The horizontal branch ( HB ) shows many RR Lyrae and red HB stars .
Comparing the CMD with [ Fe/H ] = -2.0 and [ \alpha /Fe ] = +0.3 alpha-enhanced BaSTI isochrones indicates a mean age of 12.5 Gyr for the main event and a mean age of 10.5 Gyr for the brighter SGB .
With such multiple star formation events Crater II shows similarity to more massive dwarfs that have intermediate age populations , however for Crater II there was early quenching of the star formation and no intermediate age or younger stars are present .
The spatial distribution of Crater II stars overall is elliptical in the plane of the sky , the detailed distribution shows a lack of strong central concentration , and some inhomogeneities .
The 10.5 Gyr subgiant and upper main sequence stars show a slightly higher central concentration when compared to the 12.5 Gyr population .
Matching to Gaia DR2 we find the proper motion of Crater II : \mu _ { \alpha } \cos \delta =-0.14 \pm 0.07 , \mu _ { \delta } =-0.10 \pm 0.04 mas yr ^ { -1 } , approximately perpendicular to the semi-major axis of Crater II .
Our results provide constraints on the star formation and chemical enrichment history of Crater II , but can not definitively determine whether or not substantial mass has been lost over its lifetime .