HONOLULU (AP) — More than 2,500 astronomers from around the world are descending on Hawaii for a conference at a time when telescope construction is a sensitive issue in the state. The International Astronomical Union's general assembly starts Monday. It was planned years in advance but is happening amid protests against the building of telescopes atop two mountains held sacred by Native Hawaiians. Some demonstrators on Maui and the Big Island were arrested Friday as scientists from more than 75 countries headed to Hawaii for the meetings. The protests gained momentum in April when workers tried to start construction on the Big Island's Mauna Kea of what would be one of the world's largest telescopes.