@Dev-team Suddenly cmake is confused because it does not find stellarsolver. I added the path to libstellarsolver.so to the file /usr/lib/x86_64-linux-gnu/cmake/StellarSolver/StellarSolverConfig.cmake set_target_properties(StellarSolver::stellarsolver PROPERTIES INTERFACE_INCLUDE_DIRECTORIES "/usr/include/libstellarsolver" INTERFACE_LINK_LIBRARIES "/usr/lib/x86_64-linux-gnu/libstellarsolver.so;/usr/lib/x86_64-linux-gnu/libcfitsio.so;/usr/lib/x86_64-linux-gnu/libgsl.so;/usr/lib/x86_64-linux-gnu/libgslcblas.so;/usr/lib/x86_64-linux-gnu/libwcs.so;Qt5::Core;Qt5::Network;Qt5::Widgets;Qt5::Concurrent;-lpthread" ) And now Qt Creator complains: The imported target "StellarSolver::stellarsolver" references the file "/usr/lib/x86_64-linux-gnu/libstellarsolver.so.1.5" In the directory are 3 files: libstellarsolver.so -> libstellarsolver.so.1 libstellarsolver.so.1 -> libstellarsolver.so.1.6 libstellarsolver.so.1.6 So the version 1.6 should be referenced.Read More...