Package astronomy-backgrounds-1.0-1.fc11.noarch.rpm contains an XML file /usr/share/gnome-background-properties which is a directory in other -backgrounds packages, such as gnome-backgrounds, desktop-backgrounds-basic and solar-backgrounds. It looks very much as if astronomy-backgrounds should rename that file to: /usr/share/gnome-background-properties/astronomy-backgrounds.xml
Additionally, none of the background images was installed correctly either. Fixed committed to devel (F-12).