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