Did Tycho (Or His Assistants) manipulate his observations? An analysis of Tycho’s table of mars mean oppositions

Abstract

This paper provides a detailed analysis of the Opposition Table published by Johannes Kepler in Chapter 8 of Astronomia Nova, which was originally constructed by Tycho Brahe. A preliminary study of these tables was carried out by Stephenson (1987); the present paper builds on that contribution by offering a more comprehensive analysis. The study identifies evidence suggesting that the table was assembled in two distinct phases: one preceding the pivotal observation of 1595 and another following it. This chronological division reveals that Tycho’s non-bisected Mars model was already in use by 1595. Furthermore, adjustments in the pre-1595 observations appear to have been made to align them more closely with the predictions of this model. The Opposition Table is demonstrated to be a critical element in both validating Tycho’s non-bisected model and providing the foundational input for Kepler’s vicary hypothesis. This hypothesis subsequently led to Kepler’s derivation of his first two laws of planetary motion. The findings highlight the essential role of Tycho’s observational methods and theoretical frameworks in shaping Kepler’s revolutionary contributions to astronomy.