Left panel: CMD of stars enclosed within a circle of radius = 2.0′ centred on the centre of KK 153. Middle panel: CMD of all the stars in our field located at an angular distance larger than = 3.0′ from the centre of KK 153 (field). It is worth noting that the area of the R > 3.0′ field is more than 8.3 times the area of the R < 2.0′ circle around the galaxy. Right panel: CMD of KK 153 superimposed to the CMD of the field population. The two dashed parallel lines display our selection of candidate RGB stars of KK 153. In all the CMDs the colour intensity of the points is proportional to the local star count density (Hess diagram).