Description
This page focuses on the identification of Tycho Brahe's catalog entries. The corresponding page for Ptolemy's catalog explains in detail the constraints that I have enforced on these identifications for all catalogs.
Identifications
The cross-references collected from various editions of the catalog in the cross_*.dat files on the catalog page, as well as the ones provided by VizieR's catalog J/A+A/516/A28 (in the form of HIP numbers) and by Rawlins [1] (Bayer letters, Flamsteed numbers, and HR numbers), have been resolved and expanded here in their respective ident_*.dat files.
| File name | Description |
|---|---|
| ReadMe | File descriptions |
| ident_m.dat | Identifications according to Dreyer's edition of the manuscript catalog |
| ident_b.dat | Identifications according to Baily's edition of Kepler's version |
| ident_z.dat | Identifications according to Flamsteed's version of Tycho's catalog |
| ident_f.dat | Identifications according to Flamsteed's own catalog |
| ident_a.dat | Identifications according to VizieR J/A+A/516/A28 |
| ident_r.dat | Identifications according to Rawlins [1] |
| ident_o.dat | Identifications retained for the maps etc. |
| notes_id.dat | Explanation of some identification choices in ident_o.dat |
The file ident_o.dat contains the identifications that I have retained for the maps and to establish cross-references to other catalogs. The file notes_id.dat comments on some of my choices. I have followed one author or another in most cases, and tried to remain consistent with my identification choices for other catalogs.
Cross-references
The files below cross-reference Tycho's catalog with a few others (Ptolemy, Hevelius, Flamsteed) and with the reference star set, according to the identifications in ident_o.dat and similar identification files for the other catalogs (and found on their respective pages). They are described in ReadMe.
| File name | Explanation |
|---|---|
| tycpto_oo.dat | Cross-references to Ptolemy's catalog |
| tychev_oo.dat | Cross-references to Hevelius's catalog |
| tycflm_o.dat | Cross-references to Flamsteed's catalog |
| tycref_o.dat | Cross-references to the reference star set |
Explanations about the structure of these files can be found on the corresponding Ptolemy page.
Accuracy of the catalog
The file dists_mo.dat, also described in ReadMe gives the differences between Tycho's positions according to the manuscript version from Dreyer and modern positions of the corresponding stars (according to ident_o.dat) from the Hipparcos or the SAO catalog, adjusted to Tycho's epoch and equinox. The corrections from corrs_m.dat mentioned on the catalog page have been applied before computing the distances.
| File name | Explanation |
|---|---|
| dists_mo.dat | Differences between Tycho's positions and modern ones |
The file gives differences in ecliptic longitude (multiplied by the cosine of the latitude for normalization), differences in ecliptic latitude, and great circle distances, all in arcminutes. The corresponding histograms below give an idea of the overall accuracy of the catalog (data outside the range of the x axis has been discarded).
| Longitude | Latitude | Distance |
|---|---|---|
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 |
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Similar diargrams and a detailed analysis are given by R. Verbunt & R. H. van Gent [1]. I just note the peak of the distance histogram at about 2 arcminutes and use it as a rough measure of the precision of the catalog. Tycho Brahe improves the precision by an order of magnitude over Ptolemy and Ulugh Beg.
References
[1] F. Verbunt & R. H. van Gent, Three editions of the star catalogue of Tycho Brahe, Astronomy & Astrophysics 516, A28 (2010).
[2] Dennis Rawlins, Tycho’s Star Catalog, DIO, Vol. 3, October 1993.