(dew precipitators, dew collector, dew precipitator) Not to be confused with dew gatherers. colectors or precipitators are egg-shaped devices about four centimeters on the long axis. They are made of chromoplastic that turns a reflecting white when subjected to light, and reverts to transparency in darkness. The collector forms a markedly cold surface upon which dawn dew will precipitate. They are used by fremen to line concave planting depressions where they provide a small but reliable source of water.