{"id":14249,"date":"2025-06-03T16:22:52","date_gmt":"2025-06-03T10:52:52","guid":{"rendered":"https:\/\/ibexaviation.com\/pilot-training\/?p=14249"},"modified":"2025-06-14T06:51:31","modified_gmt":"2025-06-14T01:21:31","slug":"sunrise-sunset-and-twilight","status":"publish","type":"post","link":"https:\/\/ibexaviation.com\/pilot-training\/sunrise-sunset-and-twilight\/","title":{"rendered":"Sunrise Sunset and Twilight"},"content":{"rendered":"\n<h2>Sunrise &amp; Sunset<\/h2>\n\n\n\n<h3>Sunrise and Sunset<\/h3>\n\n\n\n<ul><li>The tilt of spin axis of the earth with the orbital plane results in seasonal variation in duration of daylight<\/li><li>The time of sunrise and sunset are affected by certain factors<\/li><li>A combination of Sun\u00e2\u20ac\u2122s Declination and observer\u00e2\u20ac\u2122s latitude affects the duration of daylight<\/li><li>Semi-diameter or radius of the sun also affects sunrise and sunset<\/li><li>Refraction of light in the atmosphere increases daylight time<\/li><\/ul>\n\n\n\n<h3>Effect of Sun\u00e2\u20ac\u2122s Declination on Sunrise and Sunset<\/h3>\n\n\n\n<ul><li>Declination of the sun affects the time of sunrise and sunset<\/li><li>Consider the sun\u00e2\u20ac\u2122s position in summer during northerly declination of sun<\/li><li>Sun\u00e2\u20ac\u2122s northerly declination results in longer daylight in northern hemisphere<\/li><li>Sun would be above horizon before sun reaches observer\u00e2\u20ac\u2122s meridian<\/li><li>Sun remains above horizon after sun crosses from observer\u00e2\u20ac\u2122s meridian<\/li><li>Sunrise is earlier than 0600 LMT and sunset is later than 1800 LMT<\/li><li>Declination effect would reverse in the case of southerly declination of the sun<\/li><\/ul>\n\n\n\n<h3>Effect of Latitude on Sunrise and Sunset<\/h3>\n\n\n\n<ul><li>Latitude of the observer affects the time of sunrise and sunset<\/li><li>Consider the sun\u00e2\u20ac\u2122s position in summer when sun\u00e2\u20ac\u2122s declination is 23.5 North<\/li><li>An observer at the Equator experiences equal periods of day and night<\/li><li>An observer above 66.5\u00c2\u00b0 North experiences constant daylight<\/li><li>An observer above 66.5\u00c2\u00b0 South experiences constant night time<\/li><li>Latitude effect would reverse in the case of southerly declination of the sun<\/li><\/ul>\n\n\n\n<h3>Semi-Diameter of Sun<\/h3>\n\n\n\n<ul><li>Semi-diameter of sun and atmospheric refraction affects sunrise and sunset<\/li><li>Semi diameter of the sun is 16 minutes of arc<\/li><li>Atmospheric refraction of 34 minutes of arc<\/li><\/ul>\n\n\n\n<h3>Sunrise and Visual Horizon<\/h3>\n\n\n\n<ul><li>Sensible horizon is the horizon which is tangential to the earth surface while the visual horizon is 34 minutes below the sensible horizon<\/li><li>Sun light is visible when the sun is below sensible horizon due to bending of light<\/li><li>Centre of sun at sunrise is 16 minutes of arc below visual horizon<\/li><li>Centre of sun at sunrise is 50 minutes below sensible horizon<\/li><li>At sunrise and sunset times the sun is three minutes in terms of time below the horizon<\/li><\/ul>\n\n\n\n<h3>Civil Twilight<\/h3>\n\n\n\n<ul><li>Twilight is the period of partial light before sunrise and after sunset<\/li><li>Night flying starts from end of ECT to beginning of MCT<\/li><li>Regulations prescribe half hour after sunset to half hour before sunrise<\/li><\/ul>\n\n\n\n<h3>Morning and Evening Civil Twilight<\/h3>\n\n\n\n<ul><li>Evening civil twilight is the period of sufficient light after sunset<\/li><li>ECT extends from sunset to sun at 6 degrees below sensible horizon<\/li><li>Morning civil twilight is the period of sufficient light before sunrise<\/li><li>MCT extends from sun at 6 degrees below sensible horizon to sunrise<\/li><\/ul>\n\n\n\n<h3>Nautical and Astronomical Twilight<\/h3>\n\n\n\n<ul><li>Nautical twilight is the time when sky is dark but stars and planets are visible<\/li><li>Centre of sun is between 6 to 12 degrees below sensible horizon<\/li><li>Astronomical twilight is actually total darkness and only used by astronomers<\/li><li>Centre of sun is between 12 to 18 deg below sensible horizon<\/li><\/ul>\n\n\n\n<h3>Duration of Twilight<\/h3>\n\n\n\n<ul><li>Duration of twilight varies due a combination of the Declination of the sun and Latitude of the observer<\/li><li>Altitude of the observer and Meteorological conditions also affect the twilight duration<\/li><\/ul>\n\n\n\n<h3>Value of Civil Twilight Duration<\/h3>\n\n\n\n<ul><li>Civil twilight is at minimum value if observer and sun are at the equator<\/li><li>Minimum time of civil twilight is 21 minutes at an angular distance of 5 degrees 10 minutes<\/li><\/ul>\n\n\n\n<h3>Effect of Declination on Twilight<\/h3>\n\n\n\n<ul><li>Duration of twilight increases with increase in declination of sun<\/li><li>Sun spends more than 21 minutes in the twilight zone at solstice<\/li><\/ul>\n\n\n\n<h3>Effect of Latitude on Twilight<\/h3>\n\n\n\n<ul><li>Duration of twilight increases with increase in observer\u00e2\u20ac\u2122s latitude<\/li><li>Sun spends more than 21 minutes in the twilight zone<\/li><li>Maximum duration is seen above Arctic and Antarctic circles<\/li><li>Summer sun never sets or civil twilight extends until mid-night<\/li><li>Winter sun never rises or civil twilight does not start until mid-noon<\/li><\/ul>\n\n\n\n<h3>Effect of Altitude on Twilight<\/h3>\n\n\n\n<ul><li>Sunrise, sunset and twilight published in air-almanac are for mean sea levels<\/li><li>Increase in altitude sun would rise early and set later due to increase in Visual horizon with altitude<\/li><li>Therefore, increase in altitude results in a decrease in the duration of civil twilight<\/li><li>Reduction in atmosphere at higher levels reduces refraction and hence duration of twilight<\/li><\/ul>\n\n\n\n<h3>Effect of Scattering on Twilight<\/h3>\n\n\n\n<ul><li>Volcanic eruptions increase the duration of twilight due to increase in volcanic ash pollution<\/li><li>Polluted atmosphere increases refraction due to scattering of light<\/li><\/ul>\n\n\n\n<h2>Best of luck<\/h2>\n","protected":false},"excerpt":{"rendered":"<p>Sunrise &amp; Sunset Sunrise and Sunset The tilt of spin axis of the earth with the orbital plane results in seasonal variation in duration of daylight The time of sunrise and sunset are affected by certain factors A combination of Sun\u00e2\u20ac\u2122s Declination and observer\u00e2\u20ac\u2122s latitude affects the duration of daylight Semi-diameter or radius of the sun also affects sunrise and sunset Refraction of light in the atmosphere increases daylight time Effect of Sun\u00e2\u20ac\u2122s Declination on Sunrise and Sunset Declination of the sun affects the time of sunrise and sunset Consider&hellip;<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"disable_featured_image":false},"categories":[324],"tags":[],"_links":{"self":[{"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/posts\/14249"}],"collection":[{"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/comments?post=14249"}],"version-history":[{"count":0,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/posts\/14249\/revisions"}],"wp:attachment":[{"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/media?parent=14249"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/categories?post=14249"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/tags?post=14249"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}