1. A medical viewing system ( 10 ) comprising an X-ray image acquisition device with a source of radiation ( 12 ) and an X-ray image detection module ( 16 ); a data processing unit ( 18 ) and an output device ( 19 ); wherein the data processing unit ( 18 ) is adapted for retrieving a three-dimensional image data set, generating a first two-dimensional projection of the three-dimensional image data set corresponding to a first viewing direction and for overlaying live X-ray images onto the first two-dimensional projection constituting a first view; wherein the data processing unit ( 18 ) is adapted for generating a second two-dimensional projection of the three-dimensional image data set corresponding to a second viewing direction constituting a second view; wherein a first viewing direction vector and a second viewing direction vector enclose an offset angle α; wherein the output device ( 19 ) is adapted for outputting a combination of the first view and the second view with the same scale in a side by side manner.