Re: [Celestia-developers] stars.dat
Real-time 3D visualization of space
Status: Beta
Brought to you by:
cjlaurel
From: Selden E B. Jr <se...@le...> - 2008-07-11 11:22:01
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Why not provide them in stc catalogs? revised.stc might be appropriate for some of them, if appropriate coordinates are available. Some other stc catalog if not. That way the reasons for excluding them from the main catalog plus the sources of their improved coordinates, if any, could be documented, while those who want to use only a stringent, more accurate database could easily exclude them. s. > Interesting. We definitely have to figure out a way to incorporate > these stars in Celestia. Xi UMa and Alpha Cen B are already in > nearstars.stc, so nothing special needs to be done from them. > HIP 115215 was rejected? It's unclear to me exactly what this means. > The star is real, is it not? > Xi Sco is a multiple system (at least 5 components!) with a combined > visual magnitude of 4.16--too prominent to just omit. I wonder if the > that fact that it's a multiple star system complicated the parallax > measurement. > Kappa1 Lup is even brighter than Xi Sco: vmag = 3.85 > The last two stars are fainter: > Theta2 Ser: vmag = 4.98 > Alpha CVn B: vmag = 5.60 > ...but they should still be included. > I think that we should consider relaxing the maximum allowed error in > position. Star positions are stored as single precision floating point > values, giving 23 bits of precision (not including the sign bit). > Thus, the storage format limits us to (360*60*60)/(2^23) arcseconds, > or about 154 mas. The maximum error should be half of this--still > about twice as large as the currently allowed combined error for RA > and declination. Checking SIMBAD, it looks like Kappa1 Lup would make > the cut with a relaxed position error allowance, but Theta2 Ser and > Alpha CVn B still fail. > --Chris > On Thu, Jul 10, 2008 at 3:30 PM, Andrew Tribick > <ajt...@go...> wrote: > > The 7 rejected stars at drop-levels 0 and 1 are: > > > > 55203 = ksi Uma (no measured parallax) > > 63121 = alf CVn B (large position errors) > > 71681 = alf Cen B (large position errors) > > 74376 = kap01 Lup (large position errors) > > 78727 = ksi Sco (no measured parallax) > > 92951 = tet02 Ser (large position errors) > > 115125 = HD 219834B (according to SIMBAD, rejected from HIP) > > > > Andrew > > > > 2008/7/10 Chris Laurel <cl...@gm...>: > >> Interesting--it looks like the great majority of stars are kept, but I > >> feel very uncomfortable dropping any stars that would be visible to > >> the unaided eye. Do you know what criterion is causing these bright > >> stars to be excluded at drop-level 1? It can't be parallax, and it > >> can't be a missing Vmag (otherwise we wouldn't know that the stars > >> were bright), so I guess it must be errors in position? I'll try > >> playing with the script myself now. > >> > >> --Chris > >> > >> On Thu, Jul 10, 2008 at 2:48 PM, Andrew Tribick > >> <ajt...@go...> wrote: > >>> Statistics from a modified script which adds counter for dropped > >>> bright (using Vmag<6 criterion) stars: > >>> > >>> ---------- > >>> Drop-level 0: > >>> Fix parallaxes <0.4 (including negative parallaxes), by setting parallax to 0.4. > >>> > >>> Good stars (included): 117431 > >>> Dubious stars (included): 222 > >>> Bad stars (dropped): 565 of which 7 are bright > >>> =>Total stars included: 117653 + Sun > >>> ---------- > >>> Drop-level 1 (DEFAULT) > >>> Fix parallaxes <0.4 (including negative parallaxes) of bright stars ONLY. > >>> > >>> Good stars (included): 111465 > >>> Dubious stars (included): 2024 > >>> Bad stars (dropped): 4729 of which 7 are bright > >>> =>Total stars included: 113489 + Sun > >>> ---------- > >>> Drop-level 2 > >>> Do not fix any parallaxes > >>> Good stars (included): 111426 > >>> Dubious stars (included): 2041 > >>> Bad stars (dropped): 4751 of which 29 are bright > >>> =>Total stars included: 113467 + Sun > >>> ---------- > >>> Drop-level 3 > >>> Drop dubious stars > >>> > >>> Good stars (included): 111426 > >>> Dubious+Bad stars (dropped): 6792 of which 49 are bright > >>> =>Total stars included: 111426 + Sun > >>> ---------- > >>> SVN revision 2800 > >>> stars.dat+stars.txt > >>> > >>> =>Total stars included: 112518 + Sun > >>> > >>> Andrew > >>> > >>> 2008/7/10 Chris Laurel <cl...@gm...>: > >>>> Andrew, > >>>> > >>>> This all sounds good. I'm wondering how many stars pass the criteria? > >>>> Is there a significant change from the current stars.dat? > >>>> > >>>> Also, are there any naked eye stars that get rejected for reasons > >>>> other than bad parallaxes, for example large errors in position? > >>>> > >>>> --Chris > >>>> > >>> > >> > > > ------------------------------------------------------------------------- > Sponsored by: SourceForge.net Community Choice Awards: VOTE NOW! > Studies have shown that voting for your favorite open source project, > along with a healthy diet, reduces your potential for chronic lameness > and boredom. Vote Now at http://www.sourceforge.net/community/cca08 > _______________________________________________ > Celestia-developers mailing list > Cel...@li... > https://lists.sourceforge.net/lists/listinfo/celestia-developers |