Matthew is shown looking at the heavens through a telescope. In the longer shot, however, the telescope is revealed to be clearly pointed at the wall above the window, instead of out the window. All he could have been seeing would have been a blurry image of white plasterwork, not the stars as shown.
Matthew persuades Dai to loan him his brass telescope for his homemade theodolite. Later, however, despite the fact that the telescope has not been returned, Dai is then seen running about with the brass telescope in his hand.
In the end credits, Mrs Warner is incorrectly credited as being played by 'Peter Ann Wood' (instead of Peggy Ann Wood).
Wondering what is in the sky directly overhead, Matthew consults a star chart and points to an area of the Great Bear (Ursa Major) near the arctic circle. While some parts of Ursa Major can pass directly above England, no part of England is anywhere near the arctic circle. In any case, someone as bright as Matthew ought to know that the Earth rotates and therefore no one point is constantly overhead.
After Adam is shocked into unconsciousness by one of the stones, Margaret is the only one with him, and they're a good distance from his cottage. Adam has then somehow been carried to the cottage and deposited on the sofa, which is where he wakes up. Peter's similar transport in a later scene is explained away by the presence of the doctor who examines him for concussion, but no such explanation is given here.