# Calculating sunrise/sunset times

• ScienceMan
In summary, there is a way to calculate the sunrise and sunset times at a given latitude and longitude on a specific day using mathematical equations and algorithms. The angle at which the sun rises or sets can be determined using the declination and latitude. There are also resources available such as books and spreadsheets that provide instructions on how to calculate these events.
ScienceMan
I'm not sure if this is in the right forum but I assume someone in charge can move move it if it's not. Anyway, is there an equation or algorithm or something I can use to calculate the sunrise/sunset times at a given latitude/longitude on a given day of the year (or possibly something that would give me declination so I can put zero in and solve)? I know the basics of how it works (more extreme day lengths around the solstices and at higher latitudes and the sun not rising/setting at particularly high latitudes around the solstices, etc.) but I was wondering if there was a mathematical way to figure it out. I'm also aware that there are other things that go into it but I just need what I mentioned for my purposes.

While this is going, I can give this equation which tells where ( angle ) the Sun rises ( or sets ), north or south of due East ( or west).
sin D = cos L sin ( ANGLE )
D= declination L=latitude
Now we have the when and where.

Petter Duffett-Smith wrote a book, Practical Astronomy With Your Calculator which includes algorithms for calculating sunrise and sunset, and many other astronomical events. A later version with co-author Jonathan Zwart includes instructions on using spreadsheets to calculate events. I used the former version several decades ago to write programs in Basic. It was entertaining then, archaic today, but the logic is the same.

Rob Saunders said:
Petter Duffett-Smith wrote a book, Practical Astronomy With Your Calculator

Or look up the works of Jean Meeus. He's written several books on astronomical calculation.

## What is the purpose of calculating sunrise/sunset times?

Calculating sunrise/sunset times is important for various reasons such as agriculture, astronomy, and navigation. It helps farmers determine the optimal time to plant and harvest crops, astronomers to schedule observations, and sailors to navigate their ships.

## How are sunrise/sunset times calculated?

Sunrise and sunset times are calculated based on the position of the sun in relation to the Earth. This involves taking into account the Earth's rotation, its tilt on its axis, and its orbit around the sun. The calculation also considers factors such as the observer's location, altitude, and the time of the year.

## Why do sunrise/sunset times vary from day to day?

The sunrise and sunset times vary from day to day due to the Earth's changing position in its orbit around the sun. The tilt of the Earth's axis also plays a role, causing the amount of daylight to vary throughout the year. Additionally, factors such as weather conditions and the observer's location can also affect the exact time of sunrise and sunset.

## What are the different methods for calculating sunrise/sunset times?

There are various methods for calculating sunrise and sunset times, including the geometric method, the trigonometric method, and the analytical method. These methods use different mathematical equations and algorithms to determine the exact time of sunrise and sunset.

## Are there any tools or resources available for calculating sunrise/sunset times?

Yes, there are several tools and resources available for calculating sunrise and sunset times. These include online calculators, mobile apps, and software programs that use algorithms to accurately calculate the sunrise and sunset times for a specific location. Many weather websites also provide this information for free.

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