The origin of the OCL or OClxxx(means
Open Cluster [OCl] and NOT "
Open Cluster List"), of which there are 1112 in number, comes from; Alter, G., et.al., “
Catalogue of Stellar Clusters and Associations”, 2nd Edition, Akademiai Kiada, Budapest, Hungary (1970) (The first was in 1958, with additions.)
The OCL is the number assigned to the clusters to enable a data base of information to be achieved for cluster investigations. Originally, it was a formatted card based system, which divides into open clusters (OCL), associations (ASS) and globulars (GSC).*
Frankly these ol' numbers are really only useful for research purposes and have been superseded by Lynga's numbers in "
5th Catalogue of Open Clusters" or Dias' “
New Catalog of Optically Visible Open Clusters and Candidates” (2002).
Most catalogues really prefer NGC, IC, etc.
However, best of all now much of this is now available at the
WEBDA database (
http://www.univie.ac.at/webda/ ) You can inspect the OCL data via the "Navigation" Page - typing in the cluster in question. I.e. Example :- NGC 4103 in Crux (See
http://www.univie.ac.at/webda/cgi-bi...uster=NGC+4103 )
To read the references in the OCL data, see Budapest bibliography and click on the link in "Query". Data displayed is between years or can be searched on the linked page. Because of this now being available electronically, I only recently tossed out all the cards into the recycled rubbish bin!)
Another useful site on open clusters is Dias' one entitled "
Open Clusters and Galactic Structure"
(
http://www.astro.iag.usp.br/~wilton/ ), which I occasionally use. I has heaps of links to useful papers. (other than OCL, sadly...)
You might like to read my more general open cluster page under the section "Modern Open Cluster Catalogues"
http://homepage.mac.com/andjames/Page03003.htm
Hope this helps...
Cheers
* If you have more specific questions, I'd be happy to say more.