Observatories need what cyclists need. Height, dry air, and as few people as possible, which in practice means a well-surfaced road to a summit that almost nobody drives up. Some of the best tarmac in the American southwest exists because astronomers had to get instruments to the top of a mountain.
Kitt Peak is the clean case: a state highway that runs out at the observatory gate, which shuts at four in the afternoon so the astronomers get their dark. Haleakalā climbs from a beach to a crater rim at three thousand metres. On Mount Graham the asphalt simply stops, and the telescopes are somewhere further on up the gravel.
None of these roads promises you the telescopes. All of them promise the climb.