messier_all_gdr2.zip (2MB, expands to 7 MB, 26Nov18)
This Addon for Celestia provides those Messier objects which are not in Celestia v1.6.1, including Nebulae, Stars and Open Clusters. Its positions have been updated to use values provided by Gaia DR2. (Celestia v1.6.1 already includes all of Messier's Galaxies and Globular Clusters.)