NavList:

Happy to help you out, and I'm sure others would be, too. I teach (what I believe is) the world's only class in the practice, theory, and history of Longitude by Lunars at Mystic Seaport Museum in Connecticut. I also have long-established tools for clearing lunars set up on my website. One often needs more than the raw lunar observation to get longitudes from historical observations like these. It depends on the details.

You mentioned some of the "headline" figures in the history of lunars in your post, namely James Cook, Lewis and Clark, but remember that lunars were widely used at sea by thousands of relatively ordinary navigators from the late 18th century through the middle of the 19th. They were workaday tools, contrary to their modern reputation. Lunars fell out of use at different rates in different cultures. At sea in the American maritime world, they were essentially over and done by 1850 (with increasingly rare excceptions). On land in the sort of exploratory work that Powell was doing in the American West and that British explorers were doing in Africa, lunars continued for a few more decades. It has been my experience that lunar observations like these (in this late period) frequenly went un-analyzed because they were redundant almost by the time the exploration teams got them home. Nearly anywhere worth exploring was also worth exploiting and that meant that a telegraph line would follow in short order. And GMT by telegraph is far more accurate than by lunar.

Can you post the details of Powell's observations? Or do you know of anywhere else online where they have already been posted? Thanks.

Frank Reed
Clockwork Mapping / ReedNavigation.com
Conanicut Island USA