Telescopes

The telescope is a complex and sensitive instrument which allows for viewing and measuring objects from great distances. The quality of observation depends on the lenses or mirrors, the stability of the tube, the telescope’s mount, and how easily it can be moved. The first telescopes were developed in 1608 in the Netherlands. In 1610, Galileo began making astronomical observations with a telescope, and saw the moons of Jupiter, mountains and valleys on the moon, and new fixed stars. Several of these were contrary to Aristotelian principles, which explained that the sun, moon, and stars were perfect spheres embedded in fixed concentric rings and revolved forever at fixed rates.

Lenses and Mirrors

Refracting telescopes use lenses to collect and focus the light, just like binoculars do.
Reflecting telescopes: light enters the tube and reflects off a curved mirror (the primary mirror) at the other end, before bouncing back up the tube to near the top where it reflects off a smaller mirror (the secondary mirror), which bounces the light to your eyepiece.

The usefulness of early telescopes for astronomical observation was limited by several factors. Lenses and mirrors, which were used to collect light and magnify far-away objects, were difficult and costly to make as they required expert grinding to create the shape and clarity for a telescope. In the 19th century, only a few craftsman could create clear telescope lenses for use in the more powerful telescopes needed for astronomical research.

Mounts and Positioning

Many early telescopes were very large and cumbersome, meaning they could not easily be repositioned to track astronomical features as they moved across the sky. Telescopes also required special and complex mounts. The mounting for a telescope allows the telescope to rotate around an axis so that it may follow objects across the sky. These mounts require fine tuning so that the movements are smooth and accurate. Haverford, when purchasing its second telescope, sought advice on the effects of using a smaller mount for the new telescope--Haverford was advised against this.