At the beginning of the academic year (early September), the Sterrewacht holds a “Science Day” in the de Sitterzaal. This is a full day of presentations by the faculty, postdocs, phds and masters students. This day allows you to get a broad overview of all the different topics in astronomy people are working on here in Leiden.
There are a number of talks throughout the week. Here is a quick summary:
Discovery Talks and free lunch - Every Tuesday at 12:30 in de Sitter zaal. Two 15 minute presentations on discoveries made in Leiden's Science faculty in the past week. These talks are not astronomy-specific, but are in any scientific field. And free lunch afterwards!
If you need to book a room for a journal club or meeting, email or speak to the secretaries in room 551. You can see current reservations here (but only from inside the University firewall).
The main vein of astronomy outreach at the observatory is Universe Awareness. This organization targets young children around ages 4-10 and focuses particularly on developing countries. One of its main goals is to bring the wonders of the universe to classrooms and student that typically do not get exposure to astronomy. To get involved, you can sign up as a Student Ambassador through their Ambassador Programme. They are a friendly bunch, so if you have any questions you can stop by their office in Room 400.
Check out all the other outreach activities that happen at the Sterrewacht here: Outreach
The annual Dutch Astronomy Conference (NAC for short) is a Dutch-Belgian astronomy conference that many PhDs attend, and like the NOVA fall school it is a great place to meet other PhDs and network with the astronomy community. Although the conference is organized locally, it is in English.