{"id":24,"date":"2025-06-28T04:07:30","date_gmt":"2025-06-28T03:07:30","guid":{"rendered":"https:\/\/nottagemews.uk\/utilities\/?page_id=24"},"modified":"2025-10-11T13:53:40","modified_gmt":"2025-10-11T12:53:40","slug":"sight-calculation","status":"publish","type":"page","link":"https:\/\/nottagemews.uk\/utilities\/sight-calculation\/","title":{"rendered":"Sight Calculation"},"content":{"rendered":"\n\t<section class=\"section\" id=\"section_2134480039\">\n\t\t<div class=\"bg section-bg fill bg-fill  bg-loaded\" >\n\n\t\t\t\n\t\t\t\n\t\t\t\n\n\t\t<\/div>\n\n\t\t\n\n\t\t<div class=\"section-content relative\">\n\t\t\t\n\n<div class=\"row\"  id=\"row-86874880\">\n\n\n\t<div id=\"col-946127531\" class=\"col small-12 large-12\"  >\n\t\t\t\t<div class=\"col-inner\"  >\n\t\t\t\n\t\t\t\n\n<section>\n<h2>Celestial Sight Reduction &#8211; Step by Step<\/h2>\n<h3>Step 1: Calculate True Altitude and True Zenith Distance<\/h3>\n<p>This step corrects the sextant reading to account for observer height (dip), index error, semi-diameter of the Sun, atmospheric refraction, and parallax. The corrected angle is the <strong>true altitude<\/strong>. The <strong>true zenith distance<\/strong> is then calculated as:<\/p>\n<p><code>trueZD = 90&deg; - trueAlt<\/code><\/p>\n<h3>Step 2: Calculate Computed Zenith Distance<\/h3>\n<p>This uses the estimated position (DR latitude), the declination of the celestial body, and the Greenwich Hour Angle (GHA) to calculate the <strong>computed zenith distance<\/strong> (CZD) using spherical trigonometry and the haversine formula.<\/p>\n<p><strong>Meridian Distance<\/strong> is based on whether the latitude and declination are in the same hemisphere.<\/p>\n<h3>Step 3: Calculate Intercept and Azimuth<\/h3>\n<p>The <strong>intercept<\/strong> is the difference between the computed and observed zenith distances, representing the distance (in nautical miles) from the assumed position to the line of position (LOP):<\/p>\n<p><code>intercept = (trueZD - calcZD) &times; 60<\/code><\/p>\n<p>The <strong>azimuth<\/strong> is the bearing from the observer to the celestial body, determined using spherical trigonometry.<\/p>\n<\/section>\n\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\n\t\n\n<\/div>\n\n\t\t<\/div>\n\n\t\t\n<style>\n#section_2134480039 {\n  padding-top: 30px;\n  padding-bottom: 30px;\n}\n<\/style>\n\t<\/section>\n\t\n\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-24","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/nottagemews.uk\/utilities\/wp-json\/wp\/v2\/pages\/24","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/nottagemews.uk\/utilities\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/nottagemews.uk\/utilities\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/nottagemews.uk\/utilities\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/nottagemews.uk\/utilities\/wp-json\/wp\/v2\/comments?post=24"}],"version-history":[{"count":2,"href":"https:\/\/nottagemews.uk\/utilities\/wp-json\/wp\/v2\/pages\/24\/revisions"}],"predecessor-version":[{"id":27,"href":"https:\/\/nottagemews.uk\/utilities\/wp-json\/wp\/v2\/pages\/24\/revisions\/27"}],"wp:attachment":[{"href":"https:\/\/nottagemews.uk\/utilities\/wp-json\/wp\/v2\/media?parent=24"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}