NavList:

No, I said in my talk "one degree" and that is the best one can do with the Astrocompass which is way too small for anything more accurate. I also doubt the one to two minute accuracy claimed for any of these instruments. They're much too small to allow for any accurate setting and/or reading. And they were not built bigger because then they would become too bulky.

As Geoffrey said there is a whole family of instruments basically representing the celestial and the horizon sphere on semi circles and circles. They were first proposed in the 16th century and had their heyday in the 1920s to 1940s - I assume because the advent of the airplane as the speed of planes made rapid sight reduction of celestial observations necessary. Not many of the proposed instruments were actually sold or even built, I am aware of only eight or nine - some were tested, one was supposedly used onboard "Graf Zeppelin" crossing the South Atlantic. They obviously never performed as well as their inventors claimed and were superseded by rapid inspection tables and other instruments like the Astrograph in the UK or the ARG 1 in Germany.

One of the last examples - the Zerbee Fix Finder - has been shown and discussed on the list. It was obviously tested by the US Navy, but wasn't introduced anywhere (at least there is no documented use). The reasons are obvious for all such devices: the scales are too small, the instruments are either too delicate or too bulky.

Thanks to the list I can now add another early item to my collection (of articles, patents and pictures; no actual instruments, alas).

By the way: Frank gave two interesting presentations at Greenwich on lunar distances that I would like to see in print some time.

Wolfgang
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