Welcome to PyCS3’s documentation!



PyCS3 is a software toolbox to estimate time delays between multiple images of strongly lensed quasars, from resolved light curves such as obtained by the COSMOGRAIL monitoring program. It comes in the form of a python package, and heavily depends on numpy, scipy, and matplotlib for its core functionality. The repository is on GitLab.

To measure time delays with pycs3, you’ll typically write a script calling some high-level functions provided by the package. PyCS3 allows you to compare different point estimators (including your own), without much code integration. You can follow the example notebooks to learn how to use the core functionnality of PyCS3.

If you have already read our papers, you might want to proceed with Download & Installation, or the Tutorial.


Please read this important warning about using PyCS3.

Questions ?

Feel free to post an issue on GitLab, or to contact the code authors Martin Millon, Malte Tewes and Vivien Bonvin.


Last build of this documentation : Feb 23, 2024.