When we see a lunar crater from above it\u2019s easy to think that the crater wall is uniform around the entire perimeter.<\/span><\/p>\n However, if we look at the shape of the shadows cast by a crater wall, we can get a clearer sense of the peaks and troughs along the rim.<\/p>\n For lunar observing advice, read our guide on how to observe the Moon<\/a> or sign up to receive the BBC Sky at Night Magazine e-newsletter<\/a>.<\/strong><\/em><\/p>\n If the crater has a central peak its shadows will reveal its nature too.<\/p>\n In this guide we\u2019ll show you a straightforward method to measure the shadows in lunar craters.<\/p>\n By using some simple right-angled triangle trigonometry we can calculate the height of the lunar feature casting the shadow.<\/p>\n Our equation is:<\/p>\n O = tan\u03b8<\/span> x A; where O = \u2018opposite\u2019 (ie the height of the feature), tan\u03b8<\/span> = the tangent of the Sun angle, and A = \u2018adjacent\u2019 (ie the length of the shadow).<\/span><\/strong><\/em><\/p>\n To get started all you need is a ruler, a calculator and a photo of a crater that has clear shadows.<\/p>\n You need the time and date the photo was taken, and you can use the Lunar Terminator Visualization Tool<\/a> to find out what the Sun angle was at that time, at any point on the lunar surface.<\/p>\n We used a photo of crater Theophilus taken by Alessandro Bianconi at 03:48 UT on 18 September 2011.<\/p>\n It is important to mention that our process here has been simplified.<\/p>\n This method relies on a published crater diameter so we can scale up our shadow measurement.<\/p>\n Most craters are not perfectly circular, so the published figure is an average. We only took one diameter measurement.<\/p>\n If you use this calculation for an isolated feature, you\u2019ll need to know the pixel\/kilometre ratio for the equipment used to take photo.<\/p>\n Additionally, our process doesn\u2019t take the curvature of the lunar surface into account.<\/span><\/p>\n Remember, the Moon is a sphere, so if you chose a crater that is quite central, the foreshortening effects are less apparent.<\/span><\/p>\n It can also be difficult to know exactly where the shadow starts and ends if it\u2019s located in a complex region.<\/span><\/p>\n We are only using a single measurement of a complex crater at one Sun angle and comparing that to a published figure, which will be an average value.<\/span><\/p>\n Our method brings a sense of scale to an otherwise abstract landscape. Even though it has been simplified to make the maths easier, it still yields results that are close to the published figure.<\/p>\n This project will help you to gain a deeper awareness of the lunar features<\/a> you choose to analyse.<\/p>\n By Mary McIntyre Published: Thursday, 24 February 2022 at 12:00 am The lunar surface is at its most striking when there are well-defined shadows. As well as being visually pleasing, the study of shadows cast by lunar mountains and craters can tell us a lot about these features. When we see a lunar crater from […]<\/p>\n","protected":false},"author":24,"featured_media":29780,"template":"","categories":[1],"acf":{"readingTimeMinutes":"4"},"uagb_featured_image_src":{"full":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/02\/how-to-measure-craters-on-the-moon.jpg",1837,1080,false],"thumbnail":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/02\/how-to-measure-craters-on-the-moon-150x150.jpg",150,150,true],"medium":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/02\/how-to-measure-craters-on-the-moon-300x176.jpg",300,176,true],"medium_large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/02\/how-to-measure-craters-on-the-moon-768x452.jpg",768,452,true],"large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/02\/how-to-measure-craters-on-the-moon-1024x602.jpg",800,470,true],"1536x1536":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/02\/how-to-measure-craters-on-the-moon-1536x903.jpg",1536,903,true],"2048x2048":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/02\/how-to-measure-craters-on-the-moon.jpg",1837,1080,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 Mary McIntyre Published: Thursday, 24 February 2022 at 12:00 am The lunar surface is at its most striking when there are well-defined shadows. As well as being visually pleasing, the study of shadows cast by lunar mountains and craters can tell us a lot about these features. When we see a lunar crater from…","_links":{"self":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/rss_feed\/29779"}],"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:featuredmedia":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media\/29780"}],"wp:attachment":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media?parent=29779"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/categories?post=29779"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\""Complex\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2021\/01\/2021-01-IMG_Main_20160314_200818_Theophilus-Region-b9b26a6.jpg?quality=90&resize=620%2C593"\" "\\"\"Complex\\"\/")
<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>What you need to measure craters on the Moon<\/strong><\/h2>\n
![\""Lunar\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2022\/02\/Crater-Theophilus-3d7bb98.jpg?quality=90&resize=620%2C577"\" "\\"\"Crater\\"\/")
<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>![\""A\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2022\/02\/Theophilus-Calculation-Results-66c6db3.jpg?quality=90&resize=620%2C413"\" "\\"\"Theophilus\\"")
<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>![\""Eratosthenes\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2022\/02\/12.Eratosthenes_MainakChakraborty-e92a956.jpg?quality=90&resize=620%2C365"\" "\\"\"Eratosthenes\\"\/")
<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>You will need<\/strong><\/h2>\n
Measuring crater peaks on the Moon, step-by-step<\/strong><\/h2><\/body><\/html>\n
","protected":false},"excerpt":{"rendered":"