<p>When checking the internal consistency of the Tycho-2 catalogue, I came across 254 entries in the main catalogue file that are also present in supplement 1 (the Hipparcos/Tycho-1 stars not included in Tycho-2). These entries have the same TYC1/2/3 identifiers, and the same HIP number, but they refer to different CCDM components. For all but a few cases, the A component is found in the main catalog file, while the B component is found in supplement 1.
From the description Tycho-2 catalogue guide, I would expect these stars to have at least a different TYC3 identifier. Does anybody know why these stars were not given a unique TYC identifier?</p>

<p>Brightest example: HIP 84606 (TYC 2604-1775-1)</p>

<p>I loaded the Tycho-2 catalogue into a MySQL database, the following query selects all the duplicate entries, ordered by increasing magnitude:</p>

<pre><code>SELECT tyc, MIN(HIP) AS hip, MIN(VTmag) AS mag FROM
(
    SELECT CONCAT(TYC1, '-', TYC2, '-', TYC3) AS tyc, HIP, VTmag FROM tyc2
    UNION ALL
    SELECT CONCAT(TYC1, '-', TYC2, '-', TYC3) AS tyc, HIP, VTmag FROM suppl_1
    UNION ALL
    SELECT CONCAT(TYC1, '-', TYC2, '-', TYC3) AS tyc, HIP, VTmag FROM suppl_2
) AS t1
GROUP BY tyc HAVING COUNT(tyc)&gt;1 ORDER BY mag ASC
</code></pre>

CC BY-SA 3.0
2017-01-12T10:05:13.137Z
That's indeed where I retrieved the Tycho-2 catalogue from. To be sure nothing fishy happened when I converted the raw data files to my database, I checked that the files themselves do indeed contain the duplicates as well.
Roel Zinkstok
<star-catalogues>
Duplicate entries in Tycho-2 main and supplement 1
Roel Zinkstok
# Duplicate entries in Tycho-2 main and supplement 1

(Asked by: username_0 on 2017-01-09)

When checking the internal consistency of the Tycho-2 catalogue, I came across 254 entries in the main catalogue file that are also present in supplement 1 (the Hipparcos/Tycho-1 stars not included in Tycho-2). These entries have the same TYC1/2/3 identifiers, and the same HIP number, but they refer to different CCDM components. For all but a few cases, the A component is found in the main catalog file, while the B component is found in supplement 1.
From the description Tycho-2 catalogue guide, I would expect these stars to have at least a different TYC3 identifier. Does anybody know why these stars were not given a unique TYC identifier?
Brightest example: HIP 84606 (TYC 2604-1775-1)
I loaded the Tycho-2 catalogue into a MySQL database, the following query selects all the duplicate entries, ordered by increasing magnitude:
SELECT tyc, MIN(HIP) AS hip, MIN(VTmag) AS mag FROM
(
    SELECT CONCAT(TYC1, '-', TYC2, '-', TYC3) AS tyc, HIP, VTmag FROM tyc2
    UNION ALL
    SELECT CONCAT(TYC1, '-', TYC2, '-', TYC3) AS tyc, HIP, VTmag FROM suppl_1
    UNION ALL
    SELECT CONCAT(TYC1, '-', TYC2, '-', TYC3) AS tyc, HIP, VTmag FROM suppl_2
) AS t1
GROUP BY tyc HAVING COUNT(tyc)>1 ORDER BY mag ASC

**Tags:** star-catalogues
> **Comments:**
> **username_0**: That's indeed where I retrieved the Tycho-2 catalogue from. To be sure nothing fishy happened when I converted the raw data files to my database, I checked that the files themselves do indeed contain the duplicates as well.  

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## 0 answers

