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Table 1
Position errors in ten 18th-century catalogues.
| Catalogue | Number of stars | Number | Mean | rms | St. dev. | Internal error |
| studied | retained | (rms or st.dev) | ||||
|
|
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| Flamsteed | 220 | RA: 195 | −7.0′′ | 48.2′′ | 47.8′′ | ≈40′′ |
| (from Lalande 1783) | (over 3925) | Dec: 195 | −1.9′′ | 31.3′′ | 31.3′′ | ≈25′′ |
|
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| Rømer | 88 | RA: 88 | −2.5′′ | 5.2′′ | 4.3′′ | 4.0′′ |
| (from Galle 1845) | Dec: 81 | 7.8′′ | 14.2′′ | 11.9′′ | 13′′ | |
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| La Caille, fundamental stars | 398 | RA: 388 | 1.2′′ | 6.4′′ | 6.3′′ | 5.0′′ |
| (La Caille 1757) | Dec: 388 | 2.0′′ | 4.4′′ | 4.0′′ | 3.9′′ | |
|
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| La Caille/Bailly, fundamental stars | 307 | RA: 298 | 0.3′′ | 5.9′′ | 5.9′′ | 5.7′′ |
| (Anonymous (Bailly) 1763) | Dec: 298 | 0.0′′ | 4.6′′ | 4.6′′ | 4.6′′ | |
|
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| La Caille, southern survey | 244 | RA: 228 | 10.3′′ | 22.9′′ | 20.5′′ | 22′′ |
| (La Caille 1847) | (over 9766) | Dec: 228 | 5.8′′ | 39.2′′ | 38.9′′ | 39′′ |
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| La Caille, zodiacal stars | 515 | RA: 487 | 1.2′′ | 5.6′′ | 5.6′′ | 4.2′′ |
| (Anonymous (Bailly) 1763) | Dec: 487 | 3.0′′ | 6.5′′ | 5.8′′ | 5.6′′ | |
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| Mayer, zodiacal stars | 200 | RA: 195 | 3.3′′ | 5.9′′ | 4.9′′ | 3.7′′ |
| (from Baily 1831) | (over 998) | Dec: 195 | 4.4′′ | 5.7′′ | 3.7′′ | 3.4′′ |
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| Bradley | 215 | RA: 212 | 1.4′′ | 3.1′′ | 2.8′′ | 3.0′′ |
| (from Bessel 1818) | (over 3220) | Dec: 212 | 0.3′′ | 1.8′′ | 1.8′′ | 1.8′′ |
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| Piazzi | 203 | RA: 202 | −0.7′′ | 3.2′′ | 3.1′′ | 3.2′′ |
| (Piazzi 1814) | (over 7646) | Dec: 202 | 1.5′′ | 2.4′′ | 1.9′′ | 1.8′′ |
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| Lalande | 198 | RA: 188 | −0.2′′ | 4.3′′ | 4.3′′ | 4.3′′ |
| (from Bossert 1892) | (over ≈45 000) | Dec: 188 | 1.5′′ | 4.1′′ | 3.8′′ | 4.0′′ |
Notes. Errors are given as catalogue position minus modern position. Proper motion is accounted for.
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