NavList:

For the position of alpha Centauri on July 1, 1806 as given in the
StarPilot software, Pierre wrote:
"SHA 143d 42.7'
Dec -60d 01.8' "

Merci!
And just to clarify, you took these numbers from the calculator version
of the StarPilot software, yes? I have seen the same numbers in the PC
version, and I want to confirm that the calculator version has the same
problem.

A friend of mine has been experimenting with the demo of the PC version
of StarPilot, and I asked her to write down a few test values of SHA
for some objects for the date July 1, 1806. The positions of the Sun,
Moon, and planets are solid within the error limits defined for the
product, no more than about 1/4 of a minute of arc error in position.
The positions of the stars are clearly wrong over such long periods of
time. The SHA of Pollux is off by 2.2', the SHA of Altair is off by
-1.6', Arcturus is out by 3.5', and alpha Centauri is wrong by a
whopping 21.9'. By contrast, distant stars with low proper motions have
positions which are wrong by only a tenth of a minute or arc or so:
Antares 0.1', Canopus -0.1', Rigel 0.0'.

These positional errors are directly proportional to the distance in
time from the year 2000, so I want to re-iterate that they are NOT
significant for modern navigation, only for analysis of historical
sights.

-FER


--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---