Techniques > Variations of Existing Techniques

Sunrise, Sunset and Solar Azimuth

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MoonMan:
Sorry Captain Paranoia:I have no idea of what the "NOAA model" is, I found the site, but not the model. Astro Nav Maths,or Spherical Trigonometry,  was around before the Internet, by about two millennia {Ptolemy}. Sundials use it; Quadrants use it, so do Octants & Sextants. Latitude equals the difference between the arc Tangents of [tan A secant B]  & [cos C cot D]  Where A is Altitude, C is Hour Angle, D is Declination ,  B is Azimuth. or Conversely: A is Declination, C is Azimuth, D is Altitude, B is Hour Angle,
Declination & Hour Angle are measurements related to the Earth's Orbit around the Sun, or the Year; Azimuth & Altitude are measurements related to the Earth's Axial Rotation, or the Day.

One needs to think in Space-Time; not flat, like a map.

Lyle Brotherton:
Some of the 80,000 or so words that were not included in my book (88,000 were) included a big section of bearings at Sunrise and Sunset and for two reasons:
1.   If you do not have a compass or are in an area where your compass may be unreliable.
2.   To determine your local magnetic declination if your maps are old or do not display this information.

Here is some of this copy and also the prototype of a creditcard sized tool I developed to determine where the sun will rise/set according to the time of the year. You only need to know the current date and your latitude. (The tool would need to be scaled and drawn more accurately)

We all know that the sun rises in the east and sets in the west; what is less known is that no matter where you are in the world:
•   The sun only rises true east and sets true west on two days, September 21 & March 21: The Equinoxes. 
•   The sun rises/sets north of these points from March to September.
•   The sun rises/sets south of these points from September to March.
•   The amount it rises/sets further north or south varies by location.
•   This variation is always the same for sunrise and sunset.

To determine east/west using the sun you need to use Sunrise/Sunset Chart.
1.   Using this chart find the latitude nearest to the one where you are.
2.   Read beneath your latitude the maximum amplitude of the sun.
3.   Scale the horizontal bar from 0 to this amplitude on the side of the chart with the month you are in.
4.   Draw a line from today’s date, parallel with the vertical bar of the chart.
5.   Where this line intersects on your scale is the sun’s amplitude for that day.
6.   In the Northern hemisphere, subtract this number from 90° to find sunrise and add this number to 270° to find sunset.
7.   In the Southern hemisphere, add this number to 90° to find sunrise and subtract this number from 270° to find sunset.

To ascertain local Magnetic Declination:
1.   Using the steps above determine the bearing the sun will rise or set where you are.
2.   When it rises/sets take a bearing on it.
3.   The difference between your compasses bearing and the bearing you derived from your chart is the local magnetic declination.

Using the tool.
This is the front of the credit card sized tool (possibly with a light grid overprinted on it)



This information is printed on the reverse



At 55 degrees latitude in the northern hemisphere you divide the horizontal bar into 44 equal sections.



Using todays date, in this example October the 30th, you draw a horizontal line down from the date.



From this you can easily calculate that:
Sunrise will be at 70 degrees (90-20)
Sunset will be at 280 degrees (270+20)

MoonMan:
Captain Paranoia: the only thing that comes to mind is Geocentric & Topocentric  readings: that is, the center of the Earth as the locus; or the  surface of the Earth, or Observer's locus. There is also the matter of Parallax. In reality,the difference counts only if one is taking a serious reading for Latitude & Longitude,as in an old-fashioned Lunar. For these, one needs Tables.

adi:
Are you a sailer moonman. You talk like one.

MoonMan:
adi: Last sailor in the family was a great-grandfather, from Plymouth,  & my Aunt Nancy's first two husbands [Wilhelmson Line]. I used to make sundials, that is where I got the mathematics; the rest comes from research & observation. The Lascaux Caves have some interesting conclusions inherent in the drawings in them. I also like to get out & walk in wilderness. They all come together, over time.

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