In astronomy

Astronomy

Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...

, first light is the first use of a telescope

Telescope

A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...

 (or, in general, a new instrument) to take an astronomical

Astronomy

Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...

 image after it has been constructed. This is often not the first viewing using the telescope; optical tests have likely already been performed during daylight to adjust the components. The first light image is normally of little scientific interest and is of poor quality since the various telescope elements are yet to be adjusted for optimum efficiency. Usually, a well-known and spectacular astronomical object

Astronomical object

Astronomical objects or celestial objects are naturally occurring physical entities, associations or structures that current science has demonstrated to exist in the observable universe. The term astronomical object is sometimes used interchangeably with astronomical body...

 is chosen. Despite this, a first light is always a moment of great excitement, both for the people who designed and built the telescope, and for the astronomical community.

For example, the 200-inch Hale Telescope

Hale telescope

The Hale Telescope is a , 3.3 reflecting telescope at the Palomar Observatory in California, named after astronomer George Ellery Hale. With funding from the Rockefeller Foundation, he orchestrated the planning, design, and construction of the observatory, but did not live to see its commissioning...

 saw first light January 26, 1949, targeting NGC 2261

NGC 2261

NGC 2261 is a variable nebula located in the constellation Monoceros. It is illuminated by the star R Monocerotis , which is not directly visible itself....

. under the direction of American astronomer Edwin Powell Hubble. The image was published in many magazines.

The Large Binocular Telescope

Large Binocular Telescope

Large Binocular Telescope is an optical telescope for astronomy located on Mount Graham in the Pinaleno Mountains of southeastern Arizona, and is a part of the Mount Graham International Observatory...

 had its first light with a single primary mirror on October 12, 2005, which was a view of NGC 891

NGC 891

NGC 891 is an edge-on unbarred spiral galaxy about 30 million light-years away in the constellation Andromeda. It was discovered by William Herschel on October 6 1784. The galaxy is a member of the NGC 1023 group of galaxies in the Local Supercluster...

. The second primary mirror was installed in January 2006 and became fully operational in January 2008.

In physical cosmology

Physical cosmology

Physical cosmology, as a branch of astronomy, is the study of the largest-scale structures and dynamics of the universe and is concerned with fundamental questions about its formation and evolution. For most of human history, it was a branch of metaphysics and religion...

, first light refers to the light emitted from the first generation of hyperstars, formed less than a billion years after the big bang

Big Bang

The Big Bang theory is the prevailing cosmological model that explains the early development of the Universe. According to the Big Bang theory, the Universe was once in an extremely hot and dense state which expanded rapidly. This rapid expansion caused the young Universe to cool and resulted in...

, which brought to an end cosmological dark ages,.