Chapter 3 is all about how the stars are analysed from the Earth. So here we meet all sorts of remote analysis techniques.
It starts with a look at how we can measure the distance to the stars, starting with measuring parallax. This allows distances to the nearer stars to be measured. It also discusses the proper motion of the stars, and also the radial and space velocity from these details.
Following that there is a look at how other things can be worked out. If you know the distance, you can work out the luminosity of the star. From this you can also work out things like radius, temperature and some other things. Spectroscopy features quite highly here, as there are a number of things that can be worked out from this. Radial velocity is one thing based on the Doppler shift. However there are a number of other things you can work out from this, including some clues to the mass and temperature.
This leads to the categorisation of stars into the stellar classes such as O,B,A,F,G,K,M etc.