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Navigation Exercise 2 - Revision history
2026-07-22T15:42:30Z
Revision history for this page on the wiki
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Stephen: Text replacement - "°" to "°"
2024-02-08T20:19:30Z
<p>Text replacement - "°" to "°"</p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 20:19, 8 February 2024</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Seasonal Declination==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Seasonal Declination==</div></td></tr>
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Stephen
https://dq-nz.org/dqwiki/index.php?title=Navigation_Exercise_2&diff=43676&oldid=prev
Andreww: /* Seasonal Declination */
2007-11-24T00:21:57Z
<p><span dir="auto"><span class="autocomment">Seasonal Declination</span></span></p>
<p><b>New page</b></p><div>[[Navigation Contents |Contents]] | [[Navigation Glossary |Glossary]] | [[Navigation Exercise 1 |<< Previous Chapter]] | [[Navigation Exercise 3| Next Chapter >>]] [[Category: Regiment for the Sea]] __NOTOC__<br />
<br />
No matter where you are the Sun will follow the same path through the sky at the same time each year. There are a series of easy formulae you can use to find the bearing and altitude of the Sun at any time, and the time and bearing of sunrise and sunset for the current day.<br />
<br />
==You will need==<br />
* Current Latitude (negative for Southern Hemisphere)<br />
* Days from Equinox (negative during Northern Winter)<br />
* Current Time of Day<br />
* Alusia's Elliptic Tilt (23.5°)<br />
<br />
==Seasonal Declination==<br />
Here are three methods for finding the Seasonal Declination. The simpler the approximation, the greater the error. The last method may be up to 1.4 days, 25 miles or 0.4 degrees out.<br />
* Declination = the value from [[Navigation and Seasonal Declination|Chapter Five]].<br />
* Declination = ArcSine(Sine(DaysFromEquinox/91*90)*Sine(Tilt))<br />
* Declination &#8776; Sine(DaysFromEquinox)*Tilt<br />
<br />
==First Results==<br />
* Hours of Sunlight = 12 + (ArcSine(Tan(Declination)*Tan(Latitude)))/7.5<br />
* Dawn (Hours) = 12 - HoursOfSunlight/2<br />
* Dusk (Hours) = 12 + HoursOfSunlight/2<br />
* Sun Bearing at Dawn = ArcCosine(-Sine(Declination)/Cosine(Latitude))<br />
* Sun Bearing at Dusk = 360 - Sun Bearing at Dawn<br />
* Sun Elevation at Noon = (90-Latitude)+Declination<br />
<br />
==Second Results==<br />
* Day Progression = (Number of hours from Zenith) * 360 / 24<br />
* Sun X-Axis = Cosine(DayProgression)*Cosine(Declination)*Sine(Latitude) - Sine(Declination)*Cosine(Latitude)<br />
* Sun Y-Axis = -Sine(DayProgression)*Cosine(Declination)<br />
* Sun Z-Axis = Cosine(DayProgression)*Cosine(Declination)*Cosine(Latitude) + Sine(Declination)*Sine(Latitude)<br />
* ''Note'' Sun X-Axis<SUP>2</SUP> + Sun Y-Axis<SUP>2</SUP> + Sun Z-Axis<SUP>2</SUP> = 1<br />
<br />
==Final Results==<br />
* Sun Bearing = ArcTan(Sun Y-Axis / Sun X-Axis)<br />
* Sun Elevation = ArcSin(Sun Z-axis)</div>
Andreww