He took the name of his cousin Brother Jerome, by order of the Court of the Seine on 13 June 1837 and became Le François de Lalande him and his descendants.

Jérôme de Lalande took Michel to Paris after the holidays of 1780 and immediately initiated him into his favorite study, that is, telescopic observation techniques, despite having the satisfaction of seeing him take an interest in them.

Two years later, Michel's observation of a total lunar eclipse earned him the honor of seeing it published in the magazine journal des savants .

In 1789, at the age of 23, Michel Lefrançois de Lalande took over the direction of the observatory of the Military School and began a long series of observations.

L'histoire céleste française, published by Jerome de Lalande, completed ten years later, has more than 50,000 stars, almost all calculated by Michel, assisted by Marie Jeanne, his wife, named Amelie by the Duchess of Gotha.