`  == First use of ``open cluster`` ==  I've been trying to determine who coined the term ``open cluster``, but thus far I haven't had much success. It wasn't in use during the 1790s when William Herschel put out his first catalogue of clusters in use; Herschel himself used the expression ``irregular cluster``. The oldest confirmed use I could locate for ``open cluster`` was from an 1844 publication. That range would fit the time frame when John Herschel performed his early astronomy work. However, his General Catalogue of Nebulae and Clusters wasn't published until 1864.—  `