Magnificent and very clear image Eric.
Gum25 = RCW40 is about 7' across.
Here is a description of Gum 25 from: "Astronomy of the Milky Way" By Mike Inglis
http://books.google.com.au/books?id=...q5OwRjKUXxJJ9Q
http://web.mac.com/mdiastro/mikeingl...lications.html
Dunlop found the cluster D430 = Collinder 205 = Mrk18 (top right) in 1826.
He described it as: "A group of very small stars of mixed magnitudes, irregular figure, about 3' diameter."
John Herschel failed to see it, hence it is not in the NGC. Collinder and Markarian thought they found it but the credit should go to Dunlop.
http://www.univie.ac.at/webda/cgi-bi...?dirname=cr205