Venue and Lodging
The CHARA Meeting will be located at the Observatoire de Meudon near Paris, France. The meeting room is on the ground floor of the castle, which is marked as building #9 on the campus map available here. The web page also provides information on rail service to Meudon from the Montparnasse station in Paris.
There are limited hotel accommodations in Meudon, and very few AirBnB rentals are available. Booking.com lists four hotels in Meudon, but they all are more than 3 km away from the campus and without any easy public transport access. On the other hand, there are many option in the vicinity of Denfert Rochereau (near the Institut d'Astrophysique de Paris) and Montparnasse (where trains to Meudon depart). The RER train goes straight from the airport to Denfert-Rochereau and is easy to use. A commented list of hotels is available here:
A few options near the Montparnasse train station and the Denfert-Rochereau area in Paris include:
More generally, itineraries, schedules, last-minute infos etc. for public transport within the Ile de France region can be checked here.