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simple long focal length, small apeature refracters.
up to 1" (25mm) apeature, with up to about 1m focal lengths. in Galileo's time (early 1600's) that was considered pretty big. the magification was set at around 20x, as interchangeble eyepieces were not around. design wise, very simple. a tube with a lens at each end. well, two tubes. one tube inside the other, so that the length could be adjusted to focus. aberrations and glass quality issues of all sorts were a big problem, so for a while people were more concerned with building higher quality telescopes then larger telescopes.
these telescope were enough to see the moon's of jupiter, observe the surface of earths moon, and also to project sunlight onto paper to observe sunspots. it was also enough to allow people to see that there were more stars in the sky then they could have ever imagined. and see that some stars were actually "clouds".
then 70 or so years later Newton came along with the idea of using curved mirrors instead of lenses, so then the story kind of splits two ways... refractor vs reflector.
j
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