NavList:

Alexandre E Eremenko wrote:

> <>The telescope had to be quite large and heavy, including the
> tripod.

There were 45 men. Three boats were available, one of them a substantial
keelboat. The task was to survey the river. If schlepping a telescope
and tripod was what it took to carry out the survey, this was what
should have been done. Outside conjunction, the telescope would have
been set up on land on average once a week for an observation to provide
a later cross check of  the chronometer and the lunar distances. Neither
the trouble at the Great Fall, nor the extend of the Continental Divide
was foreseen.

> <>
>
>I suppose it is also very fragile.
> 
>
Not more so than a chronometer.

>Why an observatory in the US was needed?
>The eclipse times of the satellites were published by European
>observatories.
> 
>
Not with sufficient accuracy for cartographic purposes. The published
ephemeris should primarily be considered as auxiliary data for planning
the observations.

>Did not those Europeans that used the method successfully use the
>same Almanac?
> 
>

It started with Cassini's Ephemerides Bononienses Mediceorum syderum  in
1668, which were improved over the time. On lengthy expeditions, one
might have the newest tables, but not necessarily the current
ephemerides. And there is no real need for them. Again, control
observations from a known longitude were the key to success in
cartography. The same was actually true for the moon, too, and all the
other signals in the sky.

Herbert Prinz
*
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