UCAC4

giant.catalogs.ucac:

class giant.catalogs.ucac.UCAC4(directory=PosixPath('/Users/aliounis/Repos/giant_public/giant/catalogs/data/UCAC4'), include_proper_motion=True)[source]

This class provides access to the UCAC4 star catalog.

This class is a fully functional catalog for GIANT and can be used anywhere that GIANT expects a star catalog. As such, it implements the include_proper_motion to turn proper motion on or off as well as the method query_catalog() which is how stars are queried into the GIANT format. In addition, this catalog provides 2 additional methods cross_ref_tycho() and query_catalog_raw() to get the corresponding Tycho 2 record for the input stars or the raw UCAC4 records. These methods aren’t used anywhere by GIANT itself, but may be useful if you are doing some advanced analysis.

To use this class simply initialize it, pointing to the directory where the u4b and u4i catalog directories are contained. If the catalog files do not exist it will ask you if you want to download them, and if you answer yes, it will download the UCAC4 catalog (which takes a long time in most instances). Once the class is initialized, you can query stars from it using query_catalog() which will return a dataframe of the star records with GIANT_COLUMNS columns.

Parameters:

  • directory (Path | str) – The directory containing the UCAC4 data. This should contain 2 sub directories u4i and u4b.

  • include_proper_motion (bool) – A boolean flag specifying whether to apply proper motion when retrieving the stars

include_proper_motion

Apply proper motion to queried star locations to get the location at the requested time

Summary of Methods

query_catalog

This method queries stars from the catalog that meet specified constraints and returns them as a DataFrame with columns of GIANT_COLUMNS.

query_catalog_raw

This method queries stars from the catalog that meet specified constraints and returns them as a DataFrame or as an iterable of dataframes where the columns are the raw catalog files.

cross_ref_tycho

This retrieves the Tycho 2 catalog records for the requested UCAC4 star Zone, RNZ values.

dump_to_sqlite

Use this to write the catalog to a sqlite3 database in the GIANT format.

get_index_ind

This determines the location in the index that corresponds to the requested zone and block

get_zone_block

This tells you the zone and block number that correspond to a specific ra dec pair

convert_to_giant_catalog

This method converts records in the catalog format into records in the GIANT format.