The Spyglass was created as a result of an experiment by Malone to trap Dust. Malone created two lenses with a lacquer from plants growing in the mulefa world. By accident, Mary realised that when the lenses were covered with oil from the wheel pod trees and held a certain distance apart, she could see Dust. The mulefa gave Malone a tube of bamboo to which the the lenses were attached, keeping them the perfect distance.
The Amber Spyglass allowed the human eye to see Dust, as the mulefa eye can see unaided. Malone used the telescope to observe the loss of Dust in the mulefa world.