Noaa Sun Position Calculator

The NOAA Sun Position Calculator provides accurate solar position data including azimuth, elevation, and solar time for any location and date. This tool uses NOAA's official algorithms to calculate the sun's position based on geographic coordinates and time.

How to Use This Calculator

To calculate the sun's position:

Enter your latitude and longitude in decimal degrees
Select the date and time you want to calculate for
Click "Calculate" to get the sun's position data
Review the results including azimuth, elevation, and solar time
Use the chart to visualize the sun's path throughout the day

The calculator uses NOAA's official algorithms which are based on the Solar Position Algorithm for Satellite Applications (SPASA). These algorithms account for atmospheric refraction and other factors to provide accurate solar position data.

Formula Used

The calculator uses NOAA's Solar Position Algorithm which includes several key calculations:

Julian Date Calculation

The Julian Date (JD) is calculated from the Gregorian calendar date using:

JD = 367×year − ⌊(7×(year + ⌊(month + 9)/12⌋))/4⌋ + ⌊275×month/9⌋ + day + 1721013.5 + (hour + minute/60 + second/3600)/24

Solar Time Calculation

Solar time is calculated using:

Solar Time = Local Time + (4×(longitude − standard meridian) + equation of time) / 60

Solar Position Calculation

The sun's position is calculated using:

Azimuth = atan2(sin(hour angle), cos(hour angle)×sin(latitude) − tan(declination)×cos(latitude))

Elevation = asin(sin(latitude)×sin(declination) + cos(latitude)×cos(declination)×cos(hour angle))

These calculations account for the Earth's elliptical orbit, axial tilt, and other astronomical factors to provide accurate solar position data.

Worked Example

Let's calculate the sun's position for New York City (40.7128° N, 74.0060° W) on June 21, 2023 at 12:00 PM EDT.

Enter latitude: 40.7128
Enter longitude: -74.0060
Select date: June 21, 2023
Select time: 12:00 PM
Click "Calculate"

The calculator will return:

Azimuth: 180.0° (South)
Elevation: 68.3°
Solar Time: 12:00:00 PM

This means the sun is directly overhead (azimuth 180°) at an elevation of 68.3° above the horizon at solar noon on the summer solstice.

Interpreting Results

Azimuth

The azimuth is the compass direction from which the sun is shining, measured in degrees clockwise from north. Common interpretations:

0° - North
90° - East
180° - South
270° - West

Elevation

The elevation is the angle of the sun above the horizon, measured in degrees. Common interpretations:

0° - Sun is on the horizon
90° - Sun is directly overhead
Negative values - Sun is below the horizon (nighttime)

Solar Time

Solar time accounts for the Earth's elliptical orbit and axial tilt, which means solar noon does not always occur at 12:00 PM local time. The calculator shows the true solar time for accurate solar tracking.

Note: The sun's position changes throughout the day and throughout the year. The calculator provides a snapshot of the sun's position at the exact moment you specify.

Frequently Asked Questions

What is the difference between solar time and local time?

Solar time is based on the sun's position in the sky, while local time is based on the Earth's rotation. Solar time varies throughout the year due to the Earth's elliptical orbit and axial tilt, while local time remains constant.

How accurate is this calculator?

This calculator uses NOAA's official Solar Position Algorithm, which is accurate to within ±0.0003 degrees for elevation and ±0.0004 degrees for azimuth. The algorithm accounts for atmospheric refraction and other factors.

Can I use this calculator for solar panel installation?

Yes, this calculator provides the solar position data needed for optimal solar panel installation. By knowing the sun's azimuth and elevation throughout the day, you can position panels to maximize energy production.

What is the solar declination?

The solar declination is the angle between the rays of the sun and the plane of the Earth's equator. It varies throughout the year due to the Earth's axial tilt (23.44°). The declination affects the sun's elevation and azimuth at any given location.