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PostPosted: Tue, 05-07-16, 18:01 GMT 
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The first GAIA data release is scheduled for September 14th. That's still a while off, but has anyone given any thought to generating an updated stars.dat?

It'll be interesting to see how much their new distance measurements differ from the Hipparcos values. I'm sure there will be some excitement about revised cluster distances, especially the Pleiades.

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PostPosted: Tue, 05-07-16, 18:02 GMT 
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Yes, would definitely like to look at updating the star database scripts (I was thinking of doing this to make use of XHIP data, but the GAIA release for TYC2 stars is definitely another motivation here).


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PostPosted: Tue, 13-09-16, 18:20 GMT 
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Info about the upcoming Gaia data release is available at
http://www.cosmos.esa.int/web/gaia/dr1

The archive goes online tomorrow!

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PostPosted: Tue, 13-09-16, 18:24 GMT 
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Thanks, Selden. We are already waiting impatiently for all those stars!

Fridger

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PostPosted: Wed, 14-09-16, 21:07 GMT 
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Well it looks like it's released now. Taking a quick look at the data columns list, it looks like it will be necessary to spend a bit of time looking up various magnitude transformations before this is usable with Celestia/Celestia.Sci. Plus some way of estimating spectral types given BT, VT, G and parallax...


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PostPosted: Wed, 14-09-16, 21:34 GMT 
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Might you consider doing just the Hipparcos and Tycho subsets initially? For them, I'd expect the only new information would be their parallax values.

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PostPosted: Wed, 14-09-16, 21:51 GMT 
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This is exactly the subset I will be looking at.

The Gaia catalogue only supplies Gaia magnitudes, which we need to convert to V magnitudes. I need to look further into the Gaia magnitude system to determine what the appropriate conversion would be. TYC2 provides BT and VT, these are not quite the same as B and V but magnitude transformations have been published so at least we have something to go on here. The question is whether the Gaia magnitudes can also be incorporated into the transformation.

Spectral types are available in neither catalogue. The easy option is to use Celestia's "?" type which basically assumes A5V (you can override these properties via an .stc file with Temperature and BoloCorrection properties, not sure if they made it into released Celestia or just the SVN, nevertheless that's not a practical solution for the number of stars being considered here). The remaining options are to find a sufficiently comprehensive source that can be cross-referenced, or to work from colour indices and approximate from there.


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PostPosted: Wed, 14-09-16, 22:38 GMT 
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Sorry. I had rashly assumed that the spectral types and magnitudes were included in those catalogs.

One way to get the information for some of the stars would be to use the script interface to Aladdin. Of course, that'd take a while for 2 million stars and I suspect that many (most?) of them haven't been cataloged there.

FWIW, spectral types for 351,863 stars in the Tycho-2 catalog are available in
http://cdsarc.u-strasbg.fr/viz-bin/Cat?III/231

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PostPosted: Thu, 15-09-16, 6:33 GMT 
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The Gaia release has been all over our news today, and it looks like the BBC has already produced some graphics based on the dataset.

I'm hopeful that one day (sooner or later) we will be able to load enough of these stars into Celestia to be able to retire t00fri's sprite map of the Milky Way's sprial arms.
(Don't take it personally Fridger. ;) )

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PostPosted: Thu, 15-09-16, 7:23 GMT 
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chuft-captain wrote:
I'm hopeful that one day (sooner or later) we will be able to load enough of these stars into Celestia to be able to retire t00fri's sprite map of the Milky Way's sprial arms.
(Don't take it personally Fridger. ;) )


My old Sprite map of the Milky Way in Celestia is retired since a number of years ;-) ==> celestia.Sci

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PostPosted: Thu, 15-09-16, 7:42 GMT 
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Selden wrote:
FWIW, spectral types for 351,863 stars in the Tycho-2 catalog are available in
http://cdsarc.u-strasbg.fr/viz-bin/Cat?III/231

Thanks, that'll be useful for that subset of stars. Nevertheless the majority of stars (~1.7 million) will still lack spectral types, so definitely need to figure something out...


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PostPosted: Thu, 15-09-16, 11:28 GMT 
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http://cdsarc.u-strasbg.fr/viz-bin/Cat?I/280

contains B,V magnitudes and spectral types. It isn't clear from the description how many entries have been augmented with that info.

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PostPosted: Thu, 15-09-16, 12:06 GMT 
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t00fri wrote:
My old Sprite map of the Milky Way in Celestia is retired since a number of years ;-) ==> celestia.Sci

Oh really? Having not seen Celestia.Sci in the flesh, I was not ware of this ... but this begs the question: what did you replace it with? (Prior to GAIA I was not aware of any catalogues large enough to priovide a decent rendering of the Milky Way using star data alone.

... or perhaps you used stochastic methods to populate with fictional stars?

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PostPosted: Thu, 15-09-16, 13:01 GMT 
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chuft-captain wrote:
t00fri wrote:
My old Sprite map of the Milky Way in Celestia is retired since a number of years ;-) ==> celestia.Sci

Oh really? Having not seen Celestia.Sci in the flesh, I was not ware of this ... but this begs the question: what did you replace it with? (Prior to GAIA I was not aware of any catalogues large enough to priovide a decent rendering of the Milky Way using star data alone.


CC,

if you have a big, nicely calibrated monitor, then...have a look in the dark:
[click on images by all means and then on the fullscreen button of your browser (FF => F11)]
Attachment:
MW_2Mstars.jpg
MW_2Mstars.jpg [ 180.22 KiB | Viewed 709 times ]

Just the Milky Way with 2 million (non-GAIA foreground stars). They are available at Motherlode (Grant Hutchison et al., http://www.celestiamotherlode.net/creat ... _1.4.0.zip) and involve assumptions about spectral properties etc. The MilkyWay is the famous one by Nick Risinger sitting on a transparent sphere with the Sun in the center. The MW has the highest resolution he has granted us free of charge ;-) and is very accurate )The 2M stars are numberwise in the same ball park as what we can expect from GAIA in the near future!

Or here with Pluto + Charon:
[click on image by all means and then on the fullscreen button of your browser (FF => F11)]
Attachment:
MW_pluto_charon_2Mstars.jpg
MW_pluto_charon_2Mstars.jpg [ 236.75 KiB | Viewed 709 times ]


Of course there is also an appealing Milky Way template for views from larger distance...

Now that we are an active team of FOUR highly competent developers (Andrew, Chris( ELChristou), Dawoon, and myself) you will not have to wait very long anymore for the first beta release of celestia.Sci!. We have stable and fast 64bit versions for Windows (msvc 2015 !), MAC OS X and Linux and use the latest Qt5.7.0_64bit. + Eigen 3.x

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PostPosted: Fri, 16-09-16, 9:59 GMT 
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http://cdsarc.u-strasbg.fr/viz-bin/Cat? ... 37&menu=on

http://vizier.u-strasbg.fr/viz-bin/Vizi ... ce=I%2F337

Image
I/337
Gaia-DR1 Gaia GaiaDR1 TGAS
Gaia DR1 (Gaia Collaboration, 2016)



Code:
    Gaia Data Release 1 (DR1) contains astrometric results for more than
    1 billion stars brighter than magnitude 20.7 based on observations
    collected by the Gaia satellite during the first 14 months of its
    operational phase.

    For stars in common with the Hipparcos and Tycho-2 catalogues,
    complete astrometric single-star solutions are obtained by
    incorporating positional information from the earlier catalogues. For
    other stars only their positions are obtained, essentially by
    neglecting their proper motions and parallaxes. The results are
    validated by an analysis of the residuals, through special validation
    runs, and by comparison with external data.

    For about two million of the brighter stars (down to magnitude ∼11.5)


:)


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