Distribution Maps of Observatories
As of April 1, 2023
As of April 1, 2022
As of April 1, 2021
As of April 1, 2020
As of April 1, 2019
As of April 1, 2018
As of April 1, 2017
As of April 1, 2016
As of end of March 2015
As of end of March 2014
As of end of March 2013
As of end of March 2012
As of end of September 2011
As of end of March 2011
As of end of March 2010
As of end of March 2009
As of end of March 2008
As of end of March 2007
As of end of March 2006
As of end of March 2005