NavList:

Thanks. That's interesting. Do you happen to know what year Beta Cap was dropped?

To narrow down the search, as I said yesterday, the earliest source that I could instantly check is the Connoissance from 1790. It does not show Beta Cap. This is relevant because the French got their data from Maskelyne. Moore, The New Practical Navigator, 1800, says explicitly that the almanac lists 9 stars. Earlier editions (I checked that of 1794) do unfortunately not list the distance stars explicitly. But this in itself could be telling: Although there may have been a defacto standard, the list may not yet have been canonized.

I need to correct a statement I made yesterday. I said that the French were bolder than the English in that they tabulated Altair down to a closer distance. But I compared a Connaissance for 1845 with an Almanac for 1819. It now occurs to me that a better explanation than national character may be found in the changing latitude of the moon. The latter swinging in a band of 10 degrees causes the same swing over a period of 18 years to appear in the distance from Altair at conjunction. This influences the effect of non linearity in the rate of change of distance considerably.

It is not impossible that this kind of consideration may also have had an impact on the decision of whether to tabulate Altair or Beta Cap. What I don't understand, though, is why both stars would have been used in the same year?

Herbert Prinz