He then placed cardboard around the edges of the lens ... In striving to make images he saw through his telescope ever larger, Galileo found that his field of view became ever smaller.

The Dobsonian telescope design was developed by John ... built with inexpensive materials like plywood for the base and a cardboard or metal tube for the optical assembly and they feature fewer ...

Maybe you don't even have a telescope. No problem! I'll bet you have a cardboard box. That and a few common supplies will let you build a pinhole camera/viewer that you can use to see an eclipse ...