{"id":283,"date":"2020-10-20T19:03:54","date_gmt":"2020-10-20T19:03:54","guid":{"rendered":"https:\/\/maritimesa.org\/nautical-science-grade-11\/?p=283"},"modified":"2020-10-20T19:03:54","modified_gmt":"2020-10-20T19:03:54","slug":"reading-the-sextant","status":"publish","type":"post","link":"https:\/\/maritimesa.org\/nautical-science-grade-11\/2020\/10\/20\/reading-the-sextant\/","title":{"rendered":"Reading the sextant"},"content":{"rendered":"<p>Reading the sextant is very simple:<\/p>\n<ul>\n<li>Degrees are read directly from the graduated arc opposite the index mark on the index arm.<\/li>\n<li>Minutes are read from the micrometer drum opposite the vernier index mark.<\/li>\n<li>Seconds are read from the vernier where one of the vernier graduations lines up with one of the<br \/>\nmicrometer graduations.<\/li>\n<\/ul>\n<p>The sextant is designed to be held in the right hand whilst the forefinger and thumb of the left hand is used to move the index arm (by disengaging the clamp) and turn the micrometer drum. By moving the arm away from you, the angle on the arc is increased. Bringing it towards you, the angle is decreased. Turning the drum clockwise (as seen from the rear of the drum) the angle is increased. Turning it anti-clockwise it is decreased.<\/p>\n<div id=\"attachment_51\" style=\"width: 910px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-51\" class=\"size-full wp-image-51\" src=\"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-content\/uploads\/sites\/6\/2020\/10\/11.1.4.6_fig_1.jpg\" alt=\"\" width=\"900\" height=\"671\" srcset=\"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-content\/uploads\/sites\/6\/2020\/10\/11.1.4.6_fig_1.jpg 900w, https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-content\/uploads\/sites\/6\/2020\/10\/11.1.4.6_fig_1-300x224.jpg 300w, https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-content\/uploads\/sites\/6\/2020\/10\/11.1.4.6_fig_1-768x573.jpg 768w, https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-content\/uploads\/sites\/6\/2020\/10\/11.1.4.6_fig_1-196x146.jpg 196w, https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-content\/uploads\/sites\/6\/2020\/10\/11.1.4.6_fig_1-50x37.jpg 50w, https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-content\/uploads\/sites\/6\/2020\/10\/11.1.4.6_fig_1-101x75.jpg 101w\" sizes=\"(max-width: 900px) 100vw, 900px\" \/><p id=\"caption-attachment-51\" class=\"wp-caption-text\">Sextant reading 0\u00b0 01\u2019 10\u201d on the arc.<\/p><\/div>\n<p><strong>Reading the sextant \u201cOn\u201d and \u201cOff\u201d the arc.<\/strong>\u00a0\u00a0 When determining the index error it is necessary that one is able to read the sextant both on and off the arc. How is this done?\u00a0 First set the index arm and the micrometer drum to zero.\u00a0 By turning the drum clockwise, the graduations on the drum will increase above zero, ie 5\u2019 , 10\u2019, etc.\u00a0 By turning it anti-clockwise the reading will decrease, ie 55\u2019, 50\u2019, etc.\u00a0 In the first case the reading is positive and the angle is read directly from the drum, ie 5\u2019 on the arc.\u00a0 In the second case the reading is negative and should be deducted from 60\u2019, ie 60\u2019-55\u2019= 5\u2019 off the arc.<\/p>\n<div id=\"attachment_52\" style=\"width: 910px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-52\" class=\"size-full wp-image-52\" src=\"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-content\/uploads\/sites\/6\/2020\/10\/11.1.4.6_fig_2.jpg\" alt=\"\" width=\"900\" height=\"671\" srcset=\"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-content\/uploads\/sites\/6\/2020\/10\/11.1.4.6_fig_2.jpg 900w, https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-content\/uploads\/sites\/6\/2020\/10\/11.1.4.6_fig_2-300x224.jpg 300w, https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-content\/uploads\/sites\/6\/2020\/10\/11.1.4.6_fig_2-768x573.jpg 768w, https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-content\/uploads\/sites\/6\/2020\/10\/11.1.4.6_fig_2-196x146.jpg 196w, https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-content\/uploads\/sites\/6\/2020\/10\/11.1.4.6_fig_2-50x37.jpg 50w, https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-content\/uploads\/sites\/6\/2020\/10\/11.1.4.6_fig_2-101x75.jpg 101w\" sizes=\"(max-width: 900px) 100vw, 900px\" \/><p id=\"caption-attachment-52\" class=\"wp-caption-text\">Sextant reading 0\u00b0 01\u2019 10\u201d off the arc.<\/p><\/div>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Reading the sextant is very simple: Degrees are read directly from the graduated arc opposite the index mark on the index arm. Minutes are read from the micrometer drum opposite the vernier index mark. Seconds are read from the vernier where one of the vernier graduations lines up with one [&hellip;]<\/p>\n","protected":false},"author":6,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4,33,39],"tags":[],"class_list":["post-283","post","type-post","status-publish","format-standard","hentry","category-11-1-navigation","category-11-1-4-the-marine-sextant","category-11-1-4-6-reading-the-sextant"],"_links":{"self":[{"href":"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-json\/wp\/v2\/posts\/283"}],"collection":[{"href":"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-json\/wp\/v2\/comments?post=283"}],"version-history":[{"count":1,"href":"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-json\/wp\/v2\/posts\/283\/revisions"}],"predecessor-version":[{"id":284,"href":"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-json\/wp\/v2\/posts\/283\/revisions\/284"}],"wp:attachment":[{"href":"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-json\/wp\/v2\/media?parent=283"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-json\/wp\/v2\/categories?post=283"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-json\/wp\/v2\/tags?post=283"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}