On the rooftop was a siderostat telescope which automatically followed a star or planet across the sky.
(On the rooftop; was; a siderostat telescope which automatically followed a star or planet across the sky) (a siderostat telescope; automatically followed; a star or planet across the sky)
On the rooftop a siderostat telescope
was automatically followed
a siderostat telescope which automatically followed a star or planet across the sky
a star or planet across the sky