Telescopes weren’t invented until 1608, although lenses for eyeglasses were available from the thirteenth century onwards.
This was news to me. For some reason I just sort of assumed that astronomers maybe going back to ancient times would have had some sort of telescopes available. Quite naive of me I think, but it just goes to show that when researching a historical novel, or alternative history etc, you really need to check out your assumptions.
One of the main characters of my Hell has its Demons novel is an astronomer/astrologer by the name of Roger. Currently I am working on the plan for an early chapter of the book in which we meet Roger for the first time. As this is partly and introduction to the character I wanted the reader seeing him do what he does best – looking at the stars. Initially I thought he would be able to do this using a telescope and perhaps he would have some reference material like a book (Ptolemy‘s Almagest for instance). I even found another use he could make of the telescope later in the chapter that allowed to spy on events in a nearby village.
But… I realised that actually telescopes weren’t around then and in fact wouldn’t be until 1608. So what did astronomers use? Basically their eyes. They tended to look for good observational platforms and they also had gadgets to assist them with working out where stars should be in the sky, but that was pretty much it.
The main gadget of the astronomer was actually the astrolabe. There’s a wealth of information available about this on the internet including simulation of how it worked. This TED talk video is a particularly good introduction: