So you've never heard of the Mayans (as in the Mayan Calendars?) or the Dogon tribe? These are just two examples of ancient cultures who had stunningly accurate astronomical knowledge which has only been verified by modern science in the last 50 years thanks to Hubble etc.
A few quotes on the Dogon I've found on the net
"The Dogon Tribe lives in the Homburi Mountains near Timbuktu in the southwestern portion of the Sahara Desert in Africa. Central to their religious teachings is knowledge about the Sirius star system, which includes a star which is invisible to the naked eye and, in fact, so difficult to observe -- even through a telescope -- that no known photographs were taken of it until 1970.
The Dogon were also able to describe its elliptical orbit with Sirius A at one foci of the ellipse (an accurate description), its orbital period of 50 years (the actual figure is 50.04 +/- 0.09 years), and the fact the star rotated on its own axis (it does). Significantly, The Dogon also described a third star in the Sirius system, which they called “Emme Ya” (“Sorghum Female”), and which contained a single satellite in orbit around Emme.
The Dogon idea of their being a Sirius C, aka Emme Ya, was not accorded any real respect until 1995, when two French Astronomers published their results, after years of study, of what was apparently a small, red-dwarf star within the Sirius star system [1] The conclusion was based on perturbations in the orbits that could not be explained by any other means.
In addition to the Sirius system, The Dogon mythology includes knowledge of Saturn’s rings and Jupiter’s four major moons (none of which can be seen by the naked eye and it was only by Galileo and later astronomer’s telescopes that either could be seen). The Dogon also have long known that planets orbit the sun."
