# Millisecond pulsar timing analysis on fits file

I'm amateur to astronomy and I just want to calculate the spinning period of a pulsar (for example MAXI J0911-655) from lightcurve of it. I found Xamin then I collected data for MAXI J0911-655. Using Ciao I tried to export high sample rate lightcurve with these commands:

punlearn dmextract
pset dmextract infile="hrcf20098N001_evt2.fits[bin time=64938947.222:64938948.222:0.002]"
pset dmextract outfile="out_lc.fits"
pset dmextract opt=ltc1
pset dmextract exp="hrcf20098_000N001_dtf1.fits"
dmextract


but I got this here is the tutorial for "Basic Lightcurves"

arxiv said:

We observed X-ray pulsations at a frequency of ∼339.97 Hz

So according to the Nyquist rate, lightcurve with sampling frequency around 680 Hz is needed.

how can I have some data and calculate spinning frequency by Fast Fourier Transform?