Purbach (crater) on:
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Purbach is a large 
The crater floor is relatively smooth in the eastern half, with a low series of ridges and a partial
lunar
Lunar most commonly means "of or relating to the Moon".
Lunar may also refer to:
Arts and entertainment
* ''Lunar'' (series), a series of video games
* "Lunar" (song), by David Guetta
* "Lunar", a song by Priestess from the 2009 album ''Prior t ...
impact crater
An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters ...
located in the rugged southern highlands of the Moon
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
. The distorted crater Regiomontanus
Johannes Müller von Königsberg (6 June 1436 – 6 July 1476), better known as Regiomontanus (), was a mathematician, astrologer and astronomer of the German Renaissance, active in Vienna, Buda and Nuremberg. His contributions were instrumental ...
is attached to the southern rim. To the northwest is Thebit and just to the northeast lies La Caille
Abbé Nicolas-Louis de Lacaille (; 15 March 171321 March 1762), formerly sometimes spelled de la Caille, was a French astronomer and geodesist who named 14 out of the 88 constellations. From 1750 to 1754, he studied the sky at the Cape of Goo ...
.
Description
The outer wall of Purbach is heavily worn, with the most intact section being along the east and northeast sides. The shared rim between Purbach and Regiomontanus is incised and rugged. The wall is distorted along the western edge, giving the appearance of a double rim, with the second rim distended towards the west. The northern wall is almost completely destroyed, and somewhat irregular Purbach G lies across the northwest rim.
The crater floor is relatively smooth in the eastern half, with a low series of ridges and a partial ghost crater
A palimpsest , in planetary astronomy, is an ancient crater that has been degraded over time. They may also be referred to as "ghost craters", "degraded craters", "buried craters", or "pathological craters". Palimpsests have been identified on ...
outline just to the west of the crater midpoint. If the crater possessed a central peak, it has either been removed or forms part of the ridges to the west.
For a few hours before the first quarter, the crater's rim contributes to the "Lunar X
The Lunar X (also known as the Werner X) is a clair-obscur effect in which light and shadow creates the appearance of a letter 'X' on the rim of the Blanchinus, La Caille and Purbach craters.
The X is visible only for a few hours before the ...
" visual phenomenon, in which an 'X' shape briefly appears on the Moon's terminator
Terminator may refer to:
Science and technology
Genetics
* Terminator (genetics), the end of a gene for transcription
* Terminator technology, proposed methods for restricting the use of genetically modified plants by causing second generation s ...
as sunlight glances on the tops of shadowed hills.
Names
Purbach is named after the 15th century Austrian astronomerGeorg von Peuerbach
Georg von Peuerbach (also Purbach, Peurbach; la, Purbachius; born May 30, 1423 – April 8, 1461) was an Austrian astronomer, poet, mathematician and instrument maker, best known for his streamlined presentation of Ptolemaic astronomy in the ''Th ...
. Like many of the craters on the Moon's near side, it was named (in the Latin form, 'Purbachius') by Giovanni Riccioli
Giovanni Battista Riccioli, Society of Jesus, SJ (17 April 1598 – 25 June 1671) was an Italian astronomer and a Catholic church, Catholic priest in the Jesuit order. He is known, among other things, for his experiments with pendulums and with f ...
, whose 1651 nomenclature system has become standardized. Earlier lunar cartographers had given the feature different names: Michael van Langren's 1645 map calls it "Christierni IV Reg. Daniae", after King Christian IV of Denmark
Christian IV (12 April 1577 – 28 February 1648) was King of Denmark and Norway and Duke of Holstein and Schleswig from 1588 until his death in 1648. His reign of 59 years, 330 days is the longest of Danish monarchs and Scandinavian monar ...
, and Johannes Hevelius
Johannes Hevelius
Some sources refer to Hevelius as Polish:
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Some sources refer to Hevelius as German:
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*of the Royal Society
* (in German also known as ''Hevel''; pl, Jan Heweliusz; – 28 January 1687) was a councillor ...
grouped it with Walther
Walther is a masculine given name and a surname. It is a German form of Walter, which is derived from the Old High German ''Walthari'', containing the elements ''wald'' -"power", "brightness" or "forest" and ''hari'' -"warrior".
The name was fir ...
and Regiomontanus
Johannes Müller von Königsberg (6 June 1436 – 6 July 1476), better known as Regiomontanus (), was a mathematician, astrologer and astronomer of the German Renaissance, active in Vienna, Buda and Nuremberg. His contributions were instrumental ...
under the name "Mons Libanus", after Mount Lebanon
Mount Lebanon ( ar, جَبَل لُبْنَان, ''jabal lubnān'', ; syr, ܛܘܪ ܠܒ݂ܢܢ, ', , ''ṭūr lewnōn'' french: Mont Liban) is a mountain range in Lebanon. It averages above in elevation, with its peak at .
Geography
The Mount Le ...
.Ewen A. Whitaker, ''Mapping and Naming the Moon'' (Cambridge University Press, 1999), p. 205.
Satellite craters
By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Purbach.References
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Related article
* {{cite web, last1=Nemiroff , first1= Robert , author-link1 = Robert J. Nemiroff , last2= Bonnell , first2= Jerry , date = December 10, 2016 , url = https://apod.nasa.gov/apod/ap161210.html , title = The Lunar X , publisher = Astronomy Photo of the Day (APOD) Impact craters on the Moon