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I'm trying to develop a planetarium using Tycho 2 catalogue.

To read it I use the WCSTools. But I have a problem.

On Wikipedia I have found that Rigel star has RA: 05h 14min 32,3s and Dec: -08º 12’ 06’’. I have translate them to decimal degrees (78.6375, -8.2017). I've used that to find it on Tycho 2 catalogue (file catalog.dat) but I can't find it.

To search into the catalogue I have used the function TY2READ from ty2read.c file.

And this is how I search the star:

void ReadTy2Catalog()
{
    double raCenter = 84.5;
    double decCenter = -1.2;
    double raDistance = 10.;
    double decDistance = 10.;

    int nMaxStars = 20000;

    char* filePath = "D:\\Fuentes\\Repos\\Planetarium\\StarsCataloguesLib\\Resources\\";
    Ty2Read read;

    read.Read(
        filePath,
        TYCHO2,         /* Catalog code from wcscat.h */
        raCenter,       /* Search center J2000 right ascension in degrees */
        decCenter,      /* Search center J2000 declination in degrees */
        raDistance,     /* Search half width in right ascension in degrees */
        decDistance,    /* Search half-width in declination in degrees */
        0,              /* Limiting separation in degrees (ignore if 0) */
        0,              /* Inner edge of annulus in degrees (ignore if 0) */
        1,              /* 1 to sort stars by distance from center */
        WCS_J2000,      /* Search coordinate system */
        2000.0,         /* Search coordinate equinox */
        0.0,            /* Proper motion epoch (0.0 for no proper motion) */
        -20.0,          /* Limiting magnitudes (none if equal) */
        30.0,           /* Limiting magnitudes (none if equal) */
        1,              /* Magnitude by which to sort (1 or 2) */
        nMaxStars,      /* Maximum number of stars to be returned */
        1);             /* Verbose*/
}

I have checked all the stars returned and none has Rigel's RA and DEC.

What am I doing wrong?

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1 Answer 1

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This frustrated me as well when I first used the Tycho-2 catalog. Not finding a well known bright star can be disconcerting. Quoting from http://heasarc.nasa.gov/W3Browse/all/tycho2.html

Supplement-1 (not part of this HEASARC database but available at ftp://cdsarc.u-strasbg.fr/cats/I/259/suppl_1.dat.gz) lists stars from the Hipparcos and Tycho-1 Catalogues which are not in Tycho-2.

I only skimmed that file, but I think this might be the line you're looking for:

5331 01752 1|H|078.63446353|-08.20163919|    1.9|   -0.6|  0.6|  0.5|  0.7|  0.5| | 0.312|0.012| 0.283|0.010|999|T| 24436 

(the "-0.6" is the U-B color index, not the magntiude)

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  • $\begingroup$ Thanks. How do you read this file? Is there a library to read it? $\endgroup$
    – VansFannel
    Nov 2, 2015 at 15:30
  • $\begingroup$ I don't know about a library, but tdc-www.harvard.edu/catalogs/tycho2.format.html describes the format. $\endgroup$
    – user21
    Nov 2, 2015 at 16:14

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