1. Variable Phenomena Nyquist Sampling Harry Nyquist (1889 – 1976)

2. Consider a sine wave. How often do we need to sample it in order to figure out its frequency?

3. If we sample with a frequency which corresponds to once per wavelength, we would think the sine wave is constant

4. If we sample 1.5 times the real frequency, we’d think the function is a sine with a longer wavelength (the red curve)

5. If we sample at twice the real frequency, we get the right answer

7. Nyquist Sampling: For lossless digitization, sample at at least twice the frequency.

8. Light curves of Variable Stars Take Fourier Transform  Period

9. Phase Plot Phase, in units of cycles: