scipy is capable of doing fft-base cross-correlation, convolution, etc., but it requires the stsci package, which is not generally easy to install. For that matter, scipy can be a pain some of the time. So agpy now includes a 2D cross-correlation code and a power spectrum / power spectral density code. These are pure-numpy codes that should be easy to use without any other bothersome dependencies. EDIT: I have them check for scipy (which can cause crashes if you have a bad scipy install, e.g. 32 bit executables on a 64 bit system) because scipy uses FFTW and numpy appears not to. Also, this code & related stuff has been discussed on astrobetyter agpy correlate2d psds