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DISH SETUP: Single sat, Multi-Sat & Motorised
Traditional vs Modified Elevation/Declination Angles
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<blockquote data-quote="Hyperopia" data-source="post: 1129609" data-attributes="member: 417578"><p><strong>Modified Inclination (Elevation)/Declination</strong></p><p></p><p>After studying the subject here, and on other websites, I want to share this solution which works well for me.</p><p></p><p><strong>At the Equator:</strong></p><p>Inclination is 90°, and declination is zero, therefore no corrections are required.</p><p></p><p><strong>At the North and South poles:</strong></p><p>In theory, inclination is zero, and declination is approximately 8.6° for all angles of longitude, therefore no corrections are required.</p><p></p><p><strong>At other latitudes:</strong></p><p>Due to the offset of the antenna from the Earth N/S polar axis, the line of sight to the geostationary orbit is shortest at the due South/North satellite (depending on the hemisphere) and longest at the East/West extreme satellites. If simple inclination/declination angles are used, the antenna line of sight should correctly intercept the geostationary orbit at the due South/North satellite but will demonstrate an increasing error towards the East/West extreme satellites.</p><p></p><p><strong>Inclination/Declination corrections:</strong></p><p>(Ignoring variations in the shape of the globe) …</p><p>To mitigate the errors at 'other latitudes', a correction factor is applied to inclination and declination. This brings the antenna line of sight closer to the geostationary orbit at all visible angles of longitude regardless of the variation in distance.</p><p></p><p>I am no mathematical ninja, and after trying (and failing) to visualise the implications of the longer formulae on the website below, I settled on a simplified expression which I translated as:</p><p> Δ = 0.69 sin 2θ</p><p>and for Microsoft Excel as:</p><p> (0.69*SIN(RADIANS(2*(L))))</p><p> where L = the address of the cell containing the local latitude in degrees.</p><p></p><p>I used this formula and my limited math to build a spreadsheet which uses accepted physical constants plus the local latitude to automatically calculate the variables needed for a polar mount installation which will track the geostationary orbit well.</p><p></p><p>I'm sure that further refinements are theoretically possible, but mostly impractical due to the mechanical limitations of affordable polar mounts.</p><p></p><p>The original source of the information is:</p><p><a href="http://www.chishma.ru/antenna/modifis-polyrnaya-anten-podveska.html" target="_blank">www.chishma.ru/antenna/modifis-polyrnaya-anten-podveska.html</a></p><p> <strong>Note:</strong> It is a Russian website, but the authors acknowledge that the original solution was proposed by an English guy back in the 1970’s.</p><p></p><p>My spreadsheet looks like this:</p><p></p><p>[ATTACH=full]142334[/ATTACH]</p></blockquote><p></p>
[QUOTE="Hyperopia, post: 1129609, member: 417578"] [B]Modified Inclination (Elevation)/Declination[/B] After studying the subject here, and on other websites, I want to share this solution which works well for me. [B]At the Equator:[/B] Inclination is 90°, and declination is zero, therefore no corrections are required. [B]At the North and South poles:[/B] In theory, inclination is zero, and declination is approximately 8.6° for all angles of longitude, therefore no corrections are required. [B]At other latitudes:[/B] Due to the offset of the antenna from the Earth N/S polar axis, the line of sight to the geostationary orbit is shortest at the due South/North satellite (depending on the hemisphere) and longest at the East/West extreme satellites. If simple inclination/declination angles are used, the antenna line of sight should correctly intercept the geostationary orbit at the due South/North satellite but will demonstrate an increasing error towards the East/West extreme satellites. [B]Inclination/Declination corrections:[/B] (Ignoring variations in the shape of the globe) … To mitigate the errors at 'other latitudes', a correction factor is applied to inclination and declination. This brings the antenna line of sight closer to the geostationary orbit at all visible angles of longitude regardless of the variation in distance. I am no mathematical ninja, and after trying (and failing) to visualise the implications of the longer formulae on the website below, I settled on a simplified expression which I translated as: Δ = 0.69 sin 2θ and for Microsoft Excel as: (0.69*SIN(RADIANS(2*(L)))) where L = the address of the cell containing the local latitude in degrees. I used this formula and my limited math to build a spreadsheet which uses accepted physical constants plus the local latitude to automatically calculate the variables needed for a polar mount installation which will track the geostationary orbit well. I'm sure that further refinements are theoretically possible, but mostly impractical due to the mechanical limitations of affordable polar mounts. The original source of the information is: [URL="http://www.chishma.ru/antenna/modifis-polyrnaya-anten-podveska.html"]www.chishma.ru/antenna/modifis-polyrnaya-anten-podveska.html[/URL] [B]Note:[/B] It is a Russian website, but the authors acknowledge that the original solution was proposed by an English guy back in the 1970’s. My spreadsheet looks like this: [ATTACH type="full" width="577px"]142334[/ATTACH] [/QUOTE]
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DISH SETUP: Single sat, Multi-Sat & Motorised
Traditional vs Modified Elevation/Declination Angles
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