Astronomical Images : Optics of the concave lens

Gianbattista della Porta

Astronomical Images

<p style='text-align: justify;'>Gianbattista della Porta (1535-1615) is known for his work in natural magic and optics, and for his role in the establishment of the Accademia dei Lincei. When news of Galileo's work with the telescope began to circulate, della Porta was one of the first to react, claiming that the invention was based on his <i>De refractione</i>. Optics, however, was of considerable importance to astronomy well before the invention and application of the telescope in the seventeenth century. A typical optical problem astronomers had to tackle was atmospheric refraction, which modifies the apparent positions of celestial objects, especially near the horizon. This issue is discussed by della Porta. This figure shows how 'a thing will always appear smaller in concave lens'.</p>