http://www.iau.org
The Netherlands is a member of the IAU since 1922 and several Dutch astronomers have served as members of the IAU board. The last IAU president from the Netherlands was Lo Woltjer. The present IAU Assistant General Secretary is Dr. Karel van der Hucht (Utrecht). If you are not a member but wish to become one, the NAC should propose you. Check with Jan Lub how to go about this.