The August 2012 issue of MAINE ANTIQUES DIGEST magazine in a black & white advertisement on p. 25-A illustrates a watercolor full-body portrait of a Captain James A. Jameson probably painted circa 1845. The portrait was found on Nantucket Island, Massachusetts. The portrait shows him holding both a telescope and a sextant with a ship under sail on the horizon behind him, so he was most definitely a ship's captain. Sorry, I know no more about him.
Captain Jameson's descendants should know of this portrait. I'm scanning it and will send a digital copy by email freely to any family members who wish to have it. The Photo of the portrait was printed in black & white only on newsprint in the magazine (which is actually more like a newspaper), so it is not a perfect copy of the portrait. Nevertheless, it still is too good to be missed by the family of his descendants.
My email address may be found by clicking on my underlined name above. Please reply to me directly to this email address as I may not see a reply posted on this site. Note that there is a "dot" between both the first and last parts of my email address.
If it were a portrait of a 19th century family member in my Pease family line, I'd very much hope someone would do the same for me.