In his work De revolutionibus, Copernicus described several times his attitude towards the study of the universe. 

From ancient times until the Renaissance astronomy was orientated on the most accurate description of motions of celestial bodies observed with the naked eye: stars, and mainly planets including the Sun and the Moon.

The earliest beliefs concerning the construction of the universe come from the myths of Creation and are associated with the deification of celestial bodies. 

The astronomical interests of Copernicus developed in the period of significant progress in European astronomy, which took place in the latter part of the 15th century. A considerable contribution in this field of science was made by Georg Peurbach and Johannes Mller, also known as Regiomontanus.

While constructing his system of the world and then presenting it in De revolutionibus Copernicus made use of observations of ancient astronomers and those conducted by himself. He did that in the manner developed by Ptolemy: observational material was limited to the essential minimum required to calculate the parameters of planetary models.

The works by Copernicus on the heliocentric theory were preceded by his discovery of two principal difficulties in various versions of geocentric theories that were then recognised by astronomers, philosophers, and theologians. 

A few years after he had returned from Italy, Copernicus wrote the first draft of his heliocentric theory in a small booklet called Commentariolus most probably written in Lidzbark Warmiński (Heilsberg) around 1509.

It was not astronomical observations, even the most accurate ones, that were the basis of Copernicus astronomy, but contemplation of the harmony of the universe.