Norton's Star Atlas

Norton's Star Atlas

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Encyclopedia
Norton's Star Atlas is a set of 16 celestial charts
Star chart
A star chart is a map of the night sky. Astronomers divide these into grids to use them more easily. They are used to identify and locate astronomical objects such as stars, constellations and galaxies. They have been used for human navigation since time immemorial...

, first published in 1910 and currently in its 20th edition under the editorship of Ian Ridpath
Ian Ridpath
Ian William Ridpath is an English science writer and broadcaster made famous for his investigation and explanation of the Rendlesham Forest Incident of December 1980....

. The Star Atlas covers the entire northern and southern sky, with accompanying reference information for amateur astronomers. The charts used in the first 17 editions of the Atlas were drawn by a British schoolmaster, Arthur Philip Norton (1876–1955), after whom the Atlas was named. Norton intended his star atlas to be used in conjunction with the highly popular observing handbooks written by the British amateurs William Henry Smyth
William Henry Smyth
William Henry Smyth was an English sailor, hydrographer, astronomer and numismatist.-Private Life:...

 and Thomas William Webb
Thomas William Webb
The Reverend Thomas William Webb was a British astronomer. Some sources give his year of birth as 1806. The only son of a clergyman, the Rev. John Webb, he was raised and educated by his father, his mother having died while Thomas was a small child. He went to Oxford where he attended Magdalen...

, and consequently most of the objects featured in those guidebooks were marked on the charts. The Atlas also found favour among professional astronomers, earning it the reputation of the most widely used and best-known celestial atlas of its day.

Arrangement and projection


Norton’s Star Atlas became highly popular because of its convenient arrangement of dividing the sky into six vertical slices, or gores, like portions of a globe. Each gore covered 4 hours of right ascension
Right ascension
Right ascension is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. The other coordinate is the declination.-Explanation:...

, from declination
Declination
In astronomy, declination is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. Declination in astronomy is comparable to geographic latitude, but projected onto the celestial sphere. Declination is measured in degrees north and...

 60 degrees north to 60 degrees south, drawn on a projection specially designed by Norton. The north and south polar regions of the sky were covered by separate charts on a standard azimuthal equidistant projection
Azimuthal equidistant projection
The azimuthal equidistant projection is a type of map projection.A useful application for this type of projection is a polar projection in which all distances measured from the center of the map along any longitudinal line are accurate; an example of a polar azimuthal equidistant projection can be...

, extending from the celestial poles to declination 50 degrees north and south.

Early editions


For the first edition, Norton based his charts on the Uranométrie Générale star catalogue compiled by the Belgian astronomer Jean-Charles Houzeau
Jean-Charles Houzeau
Jean-Charles Houzeau de Lehaie was a Belgian astronomer and journalist.-Life:He was born in Havré , then in the United Kingdom of the Netherlands, later in Belgium. From 1842, he worked as a voluntary assistant at the Brussels Observatory and began writing papers. He eventually became the...

. Constellation boundaries were represented by dashed lines meandering between the stars, for no official boundaries were then established. For the 5th edition of the Atlas, published in 1933, Norton completely redrew the charts, despite now suffering from severely impaired vision in his left eye due to a blood clot behind the retina. This time he used the Harvard Revised Photometry catalogue for the positions and brightnesses of the stars. In this 5th edition the Milky Way was included for the first time, and he incorporated the official constellation boundaries that had been laid down by the International Astronomical Union
International Astronomical Union
The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...

 in 1930.

Norton redrew his charts yet again for the 9th edition published in 1943, extending the magnitude limit of the stars from 6.2 to 6.35. Positions were now given for the standard epoch
Epoch (astronomy)
In astronomy, an epoch is a moment in time used as a reference point for some time-varying astronomical quantity, such as celestial coordinates, or elliptical orbital elements of a celestial body, where these are subject to perturbations and vary with time...

 of 1950, as against 1920 previously. The 9th edition charts remained in use up to and including the 17th edition of Norton’s Star Atlas published in 1978, long after Norton’s death.

The handbook


In addition to the charts, Norton’s Star Atlas also contained a reference section featuring practical information and data of particular interest to observers. Most of this text was the work of the publisher and various expert contributors. With each passing edition, the text grew into a reference handbook as essential for amateur astronomers as the charts themselves.

Modern era


By the 1980s, Norton’s Star Atlas had come to look dated. In 1989 a totally new edition was published, the 18th, under the title Norton’s 2000.0 to emphasize that its charts had been redrawn to the new standard epoch of 2000. These charts were computer-plotted by the cartographic company of John Bartholomew and Son Ltd. in Edinburgh, Scotland, taking star positions and brightnesses from the most recent version of the Bright Star Catalogue
Bright Star Catalogue
The Bright Star Catalogue, also known as the Yale Catalogue of Bright Stars or Yale Bright Star Catalogue, is a star catalogue that lists all stars of stellar magnitude 6.5 or brighter, which is roughly every star visible to the naked eye from Earth. It is currently available online in its 5th...

, the successor to the Harvard Revised Photometry. The total number of stars plotted was over 8800, reaching to magnitude 6.5. The text was extensively rewritten and reorganized under the editorship of the British astronomy writer Ian Ridpath
Ian Ridpath
Ian William Ridpath is an English science writer and broadcaster made famous for his investigation and explanation of the Rendlesham Forest Incident of December 1980....

. For the first time in its history, Norton’s Star Atlas contained nothing by Norton himself.

A further break with the past came with the 20th edition in 2003 when publication of the title moved to New York, although the editor and contributors remained in the UK. For this edition the charts were replotted and the reference section heavily revised to reflect the latest advances in amateur astronomy.

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