Chris Lord  of Blackpool & District Astronomical Society continues the story of the telescope leading up to its use by Galileo for astronomical observations.

Ibn Sahl and Ibn al-Haythem were two scholars who during the 10th and 11th century developed the fundemental mathematical principles of refraction, reflection and dispersion and kick started the science of optics. Chris concludes this 2nd part at that point in history which marks the beginning of the telescope - Galileo's profound astronomical discoveries in 1609.