Tycho 2 Catalog

[alexis]

Good to see that you make such rapid progress! Regarding assigning HIP numbers to Tycho stars, I suggest you just add the numbers incrementally as you add the stars. That is, if the highest current Hipparcos number in the Celestia database is n, then let the new star be named n+1. And so on, for each star you add. This is not the perfect solution, but an easy way out if you don't want to modify Celestia itself. This approach also assumes that Celestia already has assigned enough bits to address the additional stars.

A better way would be to make Celestia more general in the future to allow all kind of databases. There is always a balance between versatility, complexity and effectivity of the code one has to consider, of course.

Since you already completed step 1, what is the rms error of your fit? That is, if you apply your function to the Hipparcos data, what distance error do you get, in general (comparing to the distances from "true" measured Hipparcos parallaxes)? Since there is an intrinsic spread in the data, I should caution you that there is a risk of over-fitting the data with a too-many-parameters fit (that is: don't use higher degree polynomials than you find necessary).

Keep up the good work!

/Alexis

[chris]

Good to see that you make such rapid progress! Regarding assigning HIP numbers to Tycho stars, I suggest you just add the numbers incrementally as you add the stars. That is, if the highest current Hipparcos number in the Celestia database is n, then let the new star be named n+1. And so on, for each star you add. This is not the perfect solution, but an easy way out if you don't want to modify Celestia itself. This approach also assumes that Celestia already has assigned enough bits to address the additional stars.

That's what I'd recommend also as a temporary fix . . . But, Celestia really does need a more flexible system for assigning catalog numbers. I've toyed with a couple schemes, but haven't yet found one that I like enough to switch to. I'd be more motivated if there was a wider selection of star catalogs with accurate distances--a usable Tycho catalog would be reason enough. More stars!

--Chris

[Fightspit]

I know it is an old topic but it is possible to use PMM catalogs to have more stars in celestia ?

[selden]

Celestia is 3D. It requires distances. The astronomical catlogs on that site include only the positions of stars as seen on the sky, without distances.