History of Telescope in Timeline

By Popular Timelines Editorial Team · Updated: March 29, 2025

A telescope is an instrument used to observe distant objects by detecting electromagnetic radiation they emit, absorb, or reflect. Initially, optical telescopes used lenses and/or mirrors for observing visible light. Currently, the term encompasses a broad range of instruments that can detect various parts of the electromagnetic spectrum, and even non-electromagnetic signals.

1932: Introduction of aluminized mirrors

In 1932, aluminized mirrors were introduced to reflecting telescopes, alleviating the tarnishing issues associated with speculum metal mirrors used in the 18th and early 19th centuries.

1937: First purpose-built radio telescope in operation

In 1937, the first purpose-built radio telescope went into operation, marking a significant development in astronomical instrumentation during the 20th century.

1952: Hans Wolter outlines telescope designs using glancing mirrors

In 1952, Hans Wolter outlined three ways a telescope could be built using only ring-shaped 'glancing' mirrors made of heavy metals, which are able to reflect rays at just a few degrees, as a form of X-ray optics.

2005: Record array size using space-based VLBI telescopes

As of 2005, the record array size for astronomical interferometers is many times the diameter of the Earth, achieved using space-based very-long-baseline interferometry (VLBI) telescopes like the Japanese HALCA (Highly Advanced Laboratory for Communications and Astronomy) VSOP (VLBI Space Observatory Program) satellite.

June 2008: Launch of the Fermi Gamma-ray Space Telescope

In June 2008, the Fermi Gamma-ray Space Telescope was launched. This type of telescope is usually installed on high-flying balloons or Earth-orbiting satellites.

2012: Discovery allowing focusing gamma-ray telescopes

In 2012, a discovery was made that may allow focusing gamma-ray telescopes, because at photon energies greater than 700 keV, the index of refraction starts to increase again.

2012: Launch of the NuSTAR X-ray Telescope

In 2012, the NuSTAR X-ray Telescope was launched. It uses Wolter telescope design optics at the end of a long deployable mast to enable photon energies of 79 keV.