Jos\'e Monteiro da Rocha (1734-1819) and his work of 1782 on the determination of comet orbits

In 1782 Jos\'e Monteiro da Rocha, astronomer and professor of the University of Coimbra, presented in a public session of the Royal Academy of Sciences of Lisbon a memoir on the problem of the determination of the comets' orbits. Only in 1799, the Determina\c{c}\~ao das Orbitas dos Cometas (Determination of the orbits of comets) would be published in the Academy's memoires. In that work, Monteiro da Rocha presents a method for solving the problem of the determination of the parabolic orbit of a comet from three observations. Monteiro da Rocha's method is essentially the same method proposed by Olbers and published under von Zach's sponsorship two years before, in 1797. To have been written and published in Portuguese was certainly a hindrance for its dissemination among the international astronomical community. In this article, we intend to present Monteiro da Rocha's method and trying to see to what extent Gomes Teixeira's assertion (Teixeira 1934) that Monteiro da Rocha and Olbers must figure together in the history of astronomy, as the first inventors of a practical and easy method for the determination of parabolic orbits of comets, is justified.