Go Out:  Look Up!

A Guide to the Sky, Telescopes, and Telescope Programs

The Sky's Fixed Objects - The Celestial Sphere

A good deal of the information for this page was gleaned from "History of the Discovery of the Deep Sky and "The Complete Guide to the Herschel Objects" by Mark Bratton.

The Sky since Antiquity

The sky of the ancients and the sky of today are fundamentally identical.

Most cultures grouped the bright stars into groups we call constellations or asterisms (asterisms tend to be small, cluster-like groupings). Western thought, from Greek times, believed that the fixed sky was never-changing and perfect.  Comets, which were unpredictable, were thought to be atmospheric phenomena.

Other than the stars and the Milky Way, there were few known "deep sky objects" as we currently recognized them. These included the star clusters known as the The Pleiades ("The Seven Sisters"), The Hyades (the head of Taurus the Bull), and The Beehive Cluster (M44, in Cancer) and M7 in Scorpio.

The Milky Way's satellite galaxies, known as the Large and Small Magellanic Clouds, were, of course, known to the peoples of the Southern Hemisphere, but unknown to Europeans until Magellan reported them in his travels. 

The Andromeda Galaxy (M31) and the Orion Nebula (M42), being two of the largest and brightest deep sky objects, may have been observed and well-known in other cultures (Babylonian, Mayan, etc.) but there is much uncertainty about that.

The Telescopic Sky

The Telescope was invented in 1608.  Galileo significantly improved upon existing designs (including scope having up to 33x) and in 1610 turned his scope to the sky and opened a new era in the discovery of the universe.  His observations of the craters of the moon, the phase of Venus, the moons of Jupiter and sunspots all had "earth-moving" impacts on man's view of the universe.

He did not discover new "deep sky objects", though.

The first to discover a host of new Heavenly Objects appears to have been a man named Giovanni Battista Hodierna who is credited with at least nine independent discoveries from a list he published in 1654.  His discoveries, however, were not widely received and remained largely unknown until the early 1980s.

A few new discoveries trickled in over the next 100 years before the "discovery race" began in earnest.  Philippe Loys de Chéseaux discovered a number of objects and published a catalogue in 1745-46.  Nicholas Louis de Lacaille, observing in the Southern Hemisphere, published a catalogue of many unrecorded objects in 1752.

Messier and the Messier List

Charles Messier, was a comet hunter, who, in order to avoid wasting time tracking objects that looked like comets, but were not (and therefore a waste of his time), cataloged and publish a list of deep sky objects that ultimately amounted to 109 objects.  Around forty are credited to him as discoverer, but his list made a profound impact on the astronomical community.  To this day, amateur astronomers refer to the Messier List as a starting point in observing deep sky objects.  "Messier Marathons" remain a popular event in observing clubs worldwide.

William Herschel

William Hershel was a music teach and organist who had an interest in observing and a talent for making very good (and large) reflecting telescopes.  He very systematically used his telescopes to scan the sky to find and catalog double and multiple stars.  During one scan, he discovered Uranus, the first new planet "discovered".  While he surely saw many deep sky objects during his star sweeps, he apparently was focused solely on stars.

Messier's List made an impact on him, as shortly afterwards he began systematically sweeping the skies looking for deep sky objects.  Given that he had, by far, the best telescopes of the age, he discovered and published catalogues on over 2500 deep sky objects. 

To a large degree, he, his sister, and his son essentially mapped out the entire heavens within reach of a medium sized amateur telescope.

New General and Index Catalogs

Herschel's discoveries and those of his son, John, were compiled into a number of lists that ultimately became the New General Catalog of Nebulae and Clusters of Stars containing 7,840.  Published in 1888, these objects are designated with an "NGC number".

Two later supplements referred to as the Index Catalogs and facilitated by many photographic discoveries, added  5386 new objects. These objects are designated with an "IC number."

Other Catalogs

There are a number of other catalogues available, including star catalogs, multiple star catalogues and a variety of special interest catalogs and lists (such as Arp's Catalog of Peculiar Galaxies)

Please see "History of the Discovery of the Deep Sky objects" for a very nice summary of this subject. A "discovery-by-date" table can be found at:  http://messier.seds.org/xtra/history/dis-tab.html

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Questions or comments? Email:Jeff Martin