Greetings fellow dialists, Fred Sawyer tells me that the Weir azimuth dial is a version of the universal azimuth dial deacribed by Antoine Parent in 1701. Thanks for that, Fred, I knew I could rely on you! Alas, I do not have access to the NASS publications but the BSS ones by Tony Belk that I have been referred to describe the Wulff net, which is not what Weir protrays.
It was suggested by some that the Weir diagram was a sun compass. I don't quite understand how a sun compass works. The diagram needs to be orientated N and S to work correctly which defeats the sun compass purpose. With a sun compass, as well as you latitude and the sun's declination do you need to know the time or is it self-orientating like a Foster-Lambert dial or a double horizontal dial? By the way, if anyone is interested, search for "Admiralty chart agent" and there are sources on both sides of the Atlantic which should have copies of Weir's diagram. I bought mine over the counter. Frank 55N 1W -
