Scrupulous theoretical study of 8Be nucleus states,both clustered and non-clustered,is performed over a wide range of excitation energies.The quantities that characterize the degree of the alpha-clustering of these states,i.e.,spectroscopic factors,cluster form factors,and alpha-decay widths,are computed in the framework of the de-veloped accurate ab initio approach.Other basic properties of the 8Be spectrum,including the binding and excitation energies and the mean values of the isospin,are calculated simultaneously.In the majority of instances,the results of the computation turn out to be in good agreement with the spectroscopic data.A number of predictions are made,and corresponding verification experiments are proposed.Prospects of the developed approach for nuclear spectroscopy are demonstrated.