How are Tycho stars represented in stars.dat?

[ajtribick]

On investigation into the format of stars.dat, I find that in the extended database there are stars with Hipparcos fields which are outside the range of star catalog numbers in the Hipparcos catalog.

I presume these are Tycho stars, because the starnames.dat does not contain Tycho catalog numbers as mapping from nonexistant Hipparcos numbers, yet the program identifies these.

However I identified a star in the Tycho catalog which was a duplicate, however that star does not appear to exist with even one copy, presuming that the number ABCDEFGH stored in the Hipparcos catalog field (where A-H represent single decimal digits) represents a Tycho star with catalog number ABCD-EFG-H.

So how does Celestia identify which Hipparcos numbers are Tycho stars, and how does it get the Tycho catalog number?

[selden]

chaos,

You need to read Pascal's Web page describing how the extended database was created. See the last few paragraphs on http://perso.wanadoo.fr/celestia.stars/newcat.html

I hope this helps.

[ajtribick]

Thanks, I've now identified the duplicate as TYC 2726-3367-0