Why weren the Gemini Telescopes located in Australia?
Because Australia doesn’t have any really high mountains. Ideally a telescope should be: • Far from any artificial lights. Australia does this very well. • In a region with very few clouds. The best Australian sites (Northern Flinders Ranges) are not bad in this respect (around 70% cloudless), but some overseas locations are slightly better still. • At a location free of thermals (currents of hot air in the atmosphere). These thermals blur images. Unfortunately, even the best Australian sites have quite strong thermals. The best sites overseas lie near the ocean in regions with cold ocean currents. This creates a temperature inversion which seems to lock thermals below the summits of their highest mountains, leading to very stable observing conditions and images typically twice as sharp as anywhere else. • Very high altitude.
