Nutze Skyfield fuer praezisere Daemmerungsberechnung

public/py/vendor/skyfield/data/tycho2.py

@@ -0,0 +1,51 @@
+URL = 'https://cdsarc.u-strasbg.fr/ftp/cats/I/239/tyc_main.dat'
+
+PANDAS_MESSAGE = """Skyfield needs Pandas to load the Tycho2 catalog
+
+To load the Tycho2 star catalog, Skyfield needs the Pandas data
+analysis toolkit.  Try installing it using your usual Python package
+installer, like "pip install pandas" or "conda install pandas".
+"""
+
+_COLUMN_NAMES = (
+    'Catalog', 'TYC', 'Proxy', 'RAhms', 'DEdms', 'Vmag', '---',
+    'r_Vmag', 'RAdeg', 'DEdeg', 'AstroRef', 'Plx', 'pmRA',
+    'pmDE', 'e_RAdeg', 'e_DEdeg', 'e_Plx', 'e_pmRA', 'e_pmDE', 'DE:RA',
+    'Plx:RA', 'Plx:DE', 'pmRA:RA', 'pmRA:DE', 'pmRA:Plx', 'pmDE:RA',
+    'pmDE:DE', 'pmDE:Plx', 'pmDE:pmRA', 'Nastro', 'F2', 'HIP', 'BTmag',
+    'e_BTmag', 'VTmag', 'e_VTmag', 'r_BTmag', 'B-V', 'e_B-V', '---(2)',
+    'Q', 'Fs', 'Source', 'Nphoto', 'VTscat', 'VTmax', 'VTmin', 'Var',
+    'VarFlag', 'MultFlag', 'morePhoto', 'm_HIP', 'PPM', 'HD', 'BD', 'CoD',
+    'CPD', 'Remark',
+)
+
+def load_dataframe(fobj):
+    """Given an open file for ``tyc_main.dat``, return a parsed dataframe.
+
+    If the file is gzipped, it will be automatically uncompressed.
+
+    """
+    try:
+        from pandas import read_csv
+    except ImportError:
+        raise ImportError(PANDAS_MESSAGE)
+
+    fobj.seek(0)
+    magic = fobj.read(2)
+    compression = 'gzip' if (magic == b'\x1f\x8b') else None
+    fobj.seek(0)
+
+    df = read_csv(
+        fobj, sep='|', names=_COLUMN_NAMES, compression=compression,
+        usecols=['TYC', 'Vmag', 'RAdeg', 'DEdeg', 'Plx', 'pmRA', 'pmDE'],
+        na_values=['     ', '       ', '        '],
+    )
+    df.columns = (
+        'tyc', 'magnitude', 'ra_degrees', 'dec_degrees',
+        'parallax_mas', 'ra_mas_per_year', 'dec_mas_per_year',
+    )
+    df = df.assign(
+        ra_hours = df['ra_degrees'] / 15.0,
+        epoch_year = 1991.25,
+    )
+    return df.set_index('tyc')