Which type of tool was modified to view outer space

Astronomical telescope

Explanation:

A telescope is a device used to observe object that are at distant places. It is comprised of lens or mirrors (convex or concave). Light is allowed to pass through it , producing a reflected or a refracted image. The magnification of an image is directly proportional to the len's or mirror's size. A bigger lens produces a magnified and clear image as it allows more amount of light to enter the lens, whereas a smaller lens will produce a smaller image due to its smaller amount of incident light.

Thus, an astronomical telescope is a tool extensively used to view the outer space.