Look at this photograph of one of the telescopes I use. This one's in Sodankyla in Finland and the cars give you an idea of scale. As the car on the left is 2m high, you can work out the diameter of this dish.
I need to use such a large telescope because the signals from the stars are so faint. What's more, I need to use at least two of them.
When I see a star twinkle with one telescope, I can also see it twinkle with the other, but at a different time. I know how far apart the two telescopes are and how much time elapsed between the two telescopes detecting the same event. From that I can work out how fast the compression region in the solar wind is travelling.