tycho¶
This module defines the interface to the Tycho 2 star catalogue.
Catalogue Description¶
The Tycho2 is a bright star catalogue containing positions, proper motions, and photometry for the 2.5 million brightest stars in the sky based solely on observations from the Hipparcos satellite. This corresponds to nearly complete coverage down to a visual magnitude magnitude of about 11.0.
The Tycho 2 catalogue uses a csv text file to store the stars. It is not very efficient for querying either large or
small numbers of stars. It also does not include blended stars (stars that are close enough together to appear as a
single source in an image). If you need faster retrieval and/or blended stars then you should use the
giant_catalogue instead.
For a more thorough description of the Tycho2 star catalogue see https://www.cosmos.esa.int/web/hipparcos/tycho-2.
Use¶
The Tycho 2 catalogue can be used anywhere that a star catalogue is required in GIANT. It is stored in 3 csv files plus an index csv that takes about 500 MB of disk space. If you attempt to initialize the class and point it to a directory that does not contain the Tycho 2 data it will ask you if you want to download the catalogue (note that the Tycho 2 data is not included by default so if you have not downloaded it yourself you will definitely need to). If you answer yes, be aware that it may take a very long time to download.
Once you have initialized the class (and downloaded the data files), then you can access the catalogue as you would any
GIANT usable catalogue. Simply call query_catalogue() to get the GIANT records for the stars as a
dataframe with columns according the GIANT_COLUMNS. This class also provides a helper method,
query_catalogue_raw(), which can be used to retrieve the raw catalogue entries (instead of the GIANT
entries).
Classes
This class provides access to the Tycho 2 star catalogue. |
Function
This function downloads the Tycho2 catalogue from vizier to the target directory. |