UCAC4

giant.catalogues.ucac:

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

This class provides access to the UCAC4 star catalogue.

This class is a fully functional catalogue for GIANT and can be used anywhere that GIANT expects a star catalogue. As such, it implements the include_proper_motion to turn proper motion on or off as well as the method query_catalogue() which is how stars are queried into the GIANT format. In addition, this catalogue provides 2 additional methods cross_ref_tycho() and query_catalogue_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 catalogue directories are contained. If the catalogue files do not exist it will ask you if you want to download them, and if you answer yes, it will download the UCAC4 catalogue (which takes a long time in most instances). Once the class is initialized, you can query stars from it using query_catalogue() 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

build_index

This method builds the in memory index into the catalogue files.

convert_to_giant_catalogue

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

cross_ref_tycho

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

dump_to_sqlite

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

get_from_ids

This is a generator which returns single records for each requested ID.

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

query_catalogue

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

query_catalogue_raw

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