Celestia Forums

i`ve installt 1.2.5 pre 5 and added the big stardatabas. I zoomed out of our galaxy and look back to the center of it all. and what i see is
here
is that right. or is that only on my machine?
i have a: Athlon XP 2100+, 512MB DDR, GeForce2MX400, winXPprof

well for one, it looks like you don't have your galaxy rendering turned on. second, that's what your star database should look like. there's a specific sampling error (can't remember the name now) that limits our star catalogues to those nearest to us, among other things (interstellar dust etc..).

yes its true, the galaxyrendering was turned off, here is a Screenshot with galaxyrendering on. the ?Bug? is still there. And what is the big glow in the middle of it all. In Rev. 1.2.4 it looks better, not in rings....

Those stars circles come from the limitation of the extraction procedures I used to generate the new stars database.

I will make some investigations in the source to see if something is possible to do to avoid them, but with no guarantee.

Don't forget that more than 90 % of the Tycho stars that were added to the initial stars database of Celestia don't have any meaningfull parallax values, and that their distances have been estimated only on the basis of their apparent magnitudes and color indexes.

Only the 100 000 hipparcos stars have good measured trigonometric parallaxes (by the Hipparcos satellite). It doesn't exist another catalog with more stars with known distances.

Go perhaps to my website :
http://perso.wanadoo.fr/celestia.stars/

and read what concerns the extraction procedure that has been used to generate the two new stars databases...

But I will still make some investigations in the source to see if something could be improved

Until then...

Best regards

Pascal

well, also remember how parallax is measured. in order to measure any parallax, you use background stars that don't move appreciably during the year. so you have a natural bias in your sampling limiting your catalogues to only nearby stars. but i suppose this will be fixed soon with the interferometer mission that is still in planning stages.

Questions come up frequently about whether the distance to some star or other is correct. Often the Hipparcos numbers will be off from other published values by a factor of 2 or more.

The fact is that measuring the distances to faraway stars is very, very hard, and the published distances to anything further than a few dozen light-years away, in the Celestia database or others, should be taken with a grain of salt. In many cases the Hipparcos numbers will be more accurate than older ones, but on the other hand, the parallax-based Hipparcos measurements for stars thousands of light-years away are probably not so trustworthy.

The 3D arrangement of stars in Celestia should be taken only as generally suggestive of the true arrangement, except in the Sun's immediate stellar neighborhood-- the closest few dozens of light years or so.