Obstacles encountered by four major European astronomical observatories belonging to academies in the 18th century

It is known that, in the first half of the 18th century, the conditions for astronomy at the Imperial Observatory of St-Petersburg, directed by Joseph-Nicolas Delisle, were comparable to those enjoyed by astronomers at the royal observatories of Paris and Greenwich created in the previous century. But what about the public observatories created in the first half of the 18th century in Berlin, Uppsala and Bologna? The rich correspondence maintained by Joseph-Nicolas Delisle with the astronomers working in these observatories provides elements of an answer to this question. It also provides more precise information on Delisle's working conditions at the St-Petersburg Observatory. In this article, we present a comparative analysis of the obstacles encountered by astronomers at these different observatories, and the particular contexts in which they operated, including a breakdown by observatory of salaries and expenditure on astronomy equipment.