quarter Moon<\/a>.<\/span><\/p>\nIts large size and grey floor make it easy to find, though it is not easy to spot under very high illumination.<\/span><\/p>\nThe shape of the crater is more or less circular, but the rampart is low and irregular; the highest peak, in the northwestern rim, rises to an altitude of 2.9km.<\/span><\/p>\nThe floor is flooded with lava; there is no central peak and Ptolemaeus is clearly ancient, dating back to the time of the Great Bombardment.<\/span><\/p>\n ![\""Ptolemaeus,\"]( "\\"\"Moon_Ptolemy_003\"\\"")
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Ptolemaeus, Alphonsos & Arzachel by Stephen Curling, UK. Equipment: Edge1100 SCT, CGEMDX, ZWO174mm, x2 Barlow.<\/span><\/figcaption><\/div>\nFormations of this kind are often called \u2018walled plains\u2019. The only major feature on the floor is the low-rimmed, bowl-shaped, 9km crater Ammonius (formerly known as Ptolemaeus A), which lies about 10km northeast of the centre of Ptolemaeus and is easy to see with any telescope. It is almost 2km deep. <\/span><\/p>\nUnder low illumination Ptolemaeus is magnificent, with the peaks of the rim casting shadows.<\/span><\/p>\nWhen the Sun is high, small craterlets can be seen, and there are several \u2018ghost craters\u2019 \u2013 old formations that have been overwhelmed by lava that are now barely traceable.<\/span><\/p>\nOne of these ghosts, Ptolemaeus B, is 17km across and lies just north of Ammonius.<\/span><\/p>\nThe Ptolemaeus crater chain<\/span><\/strong><\/h1>\n ![\""Ptolemaeus,\"]( "\\"\"Moon_Ptolemy_002\"\\"")
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Ptolemaeus, Alphonsos and Arzachel by Gary Thomson, S. Lanarkshire, UK. Equipment: Skywatcher 200p, HEQ5, Dmk618, x2 Barlow<\/span><\/figcaption><\/div>\nPtolemaeus is the northern member of a chain of three large formations.<\/span><\/p>\nThe central member, Alphonsus, has a low central peak and a system of rilles on its floor.<\/span><\/p>\nThe southern member, Arzachel, has higher walls and is more regular, with a prominent central peak. <\/span><\/p>\nArzachel is the smallest of the trio and is presumably the youngest.<\/span><\/p>\nTransient lunar phenomena have been reported in Alphonsus, but not in Ptolemaeus or Arzachel.<\/span><\/p>\n ![\""Ptolemaeus\"]( "\\"\"Moon_Ptolemy_001\"\\"")
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Ptolemaeus by Walter McMonagle, Epsom, UK. Equipment: Canon 650D, Celestron NexStar 5SE.<\/span><\/figcaption><\/div>\n\nDespite its smooth floor and its low walls, Ptolemaeus isn\u2019t the best choice for an early manned lunar base. It\u2019s close to the equator and here the extreme temperature variations are far from ideal.<\/span><\/p>\nYet in the future there seems no reason why a base should not be established there.<\/span><\/p>\nIt\u2019s interesting to note that from a base near the centre of the crater you would be unable to see even the loftiest peaks of the outer wall.<\/span><\/p>\nThey would be well below your horizon. But from there, our own world will be high in the sky and will look truly splendid.<\/span><\/p>\n ![\""The\"]( "\\"\"Moon_Ptolemy_004\"\\"")
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The Moon Craters by Marc Delaney, Barry, Wales, UK. Equipment: Meade-LS-ACF-6\u2033, ZWO-178MC<\/span><\/figcaption><\/div>\nNext time the sky is clear and the chain of craters, including Ptolemaeus, is sunlit, it is well worth seeking out these great walled plains.<\/span><\/p>\nBinoculars will show them clearly when the floors are partly shadowed, and with any telescope you will be able to locate them even when the Sun is high over them and there is little or no shadow.<\/span><\/p>\nCertainly Ptolemaeus, with its broken walls, smooth floor and inner ghosts, is one of the most intriguing of all the craters on the Moon.<\/span><\/p>\n\n ![\""The\"]( "\\"\"Moon_Ptolemy_005\"\\"")
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The Area Around The Crater Ptolemaeus by Steve Williams, Irthlingborough, Northants, UK. Equipment: 150mm F8 refractor, ASI120 Mono CCD.<\/span><\/figcaption><\/div>\n\n
","protected":false},"excerpt":{"rendered":"By Patrick Moore Published: Monday, 09 August 2021 at 12:00 am Ptolemaeus is one of the most famous lunar craters. It\u2019s named after Claudius Ptolemaeus (Ptolemy), who lived from about 120 AD to 180 AD and was the last and arguably the greatest of the Greek astronomers of antiquity. The crater was named by Giovanni […]<\/p>\n","protected":false},"author":24,"featured_media":0,"template":"","categories":[34],"acf":{"readingTimeMinutes":"4"},"uagb_featured_image_src":{"full":false,"thumbnail":false,"medium":false,"medium_large":false,"large":false,"1536x1536":false,"2048x2048":false},"uagb_author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/author\/importmanagerhubsprylab-com\/"},"uagb_comment_info":0,"uagb_excerpt":"By Patrick Moore Published: Monday, 09 August 2021 at 12:00 am Ptolemaeus is one of the most famous lunar craters. It\u2019s named after Claudius Ptolemaeus (Ptolemy), who lived from about 120 AD to 180 AD and was the last and arguably the greatest of the Greek astronomers of antiquity. The crater was named by Giovanni…","_links":{"self":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/rss_feed\/22059"}],"collection":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/rss_feed"}],"about":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/types\/rss_feed"}],"author":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/users\/24"}],"wp:attachment":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media?parent=22059"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/categories?post=22059"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
![\""Ptolemaeus,\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2019\/02\/moona-6c7a3a6-e1627654477588.jpg?quality=90&resize=620%2C421"\" "\\"\"Moon_Ptolemy_006\"\\"")
<\/div>![\""Ptolemaeus,\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2019\/02\/Unknown_0-7269f90.png?quality=90&resize=620%2C371"\" "\\"\"Moon_Ptolemy_003\"\\"")
<\/div>![\""Ptolemaeus,\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2019\/02\/moon-triplet-63227b8.jpg?quality=90&resize=616%2C434"\" "\\"\"Moon_Ptolemy_002\"\\"")
<\/div>![\""Ptolemaeus\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2019\/02\/Ptolemaeus-ce3e158.jpg?quality=90&resize=620%2C417"\" "\\"\"Moon_Ptolemy_001\"\\"")
<\/div>![\""The\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2019\/02\/Marc-Delaney-Moon-bcf4b54-e1627986628150.jpg?quality=90&resize=620%2C466"\" "\\"\"Moon_Ptolemy_004\"\\"")
<\/div>![\""The\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2019\/02\/Ptolemaeus_1-9d7efd7.jpg?quality=90&resize=620%2C554"\" "\\"\"Moon_Ptolemy_005\"\\"")
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