How to Calculate Sunrise by Latitude

Calculating the sunrise based on your latitude requires a complex formula. Many sites offer sunrise calculators, but many do-it-yourselfers would rather test the means of calculation to draw their own conclusions by avoiding calculators and tackling complex equations to determine the answer. Before you can effectively determine sunrise based on your latitude, you must be familiar with the days in the Julian calendar while taking into consideration distances, leap years and Daylight Savings Time.

Instructions

    • 1

      Count how many days have passed since Jan. 1, 2000 to the day you want to calculate the sunrise for. This will provide you with the variable you require to construct your equation by adding the days with 2,451,545. This number is the representing number for the Julian Jan. 1, 2000.

    • 2

      Subtract the Julian date of sunrise you wish to find out by 2,451,545. Subtract your answer from 0.0009.

    • 3

      Divide 360 by your west longitude. Although you are calculating based on your latitude coordinates, longitude is still an important factor for pinpointing the exact time of sunrise.

    • 4

      Subtract your answer from the sum of your Julian date. Once you have worked out this equation, round your answer to the nearest tenth. This gives you your Julian cycle of sunrise.

    • 5

      Divide 360 by your west longitude once again. Add your answer to 2,451,545, 0.0009 and your Julian cycle. This gives you the approximate Julian date of solar noon.

    • 6

      Determine your mean solar anomaly by adding 357.5291 with 0.98560028. Subtract 2,451,545 by your Julian solar noon and multiply your sum with your previous answer. Multiply this by your modular number based from 360 which will be an even number.

    • 7

      Multiply your mean solar anomaly by two and three. Determine the sines, or number expansion of each answer. Set your answers aside. Determine the sine of your mean solar anomaly. Multiply your answer by 1.9148. Use your mean solar anomaly times two answer to multiply by 0.0200 followed by your answer from the three multiplication being multiplied by 0.0003. This gives you your solar center.

    • 8

      Add your mean solar anomaly to 102.9372, your solar center and 180. Multiply your answer by the modular number based from 360. This will provide you with your ecliptical longitude of the sun.

    • 9

      Multiply the ecliptical longitude of the sun by two. Multiply the sine of your answer by 0.0069. Multiply the sine of your mean solar anomaly by 0.0053 and subtract your answers. Add with your approximation of the Julian date for the solar noon to solidify the exact Julian solar moon date.

    • 10

      Multiply the sine of your ecliptical longitude of the sun and the sine of 23.45. Multiply your answer by its inverse number, or arcsine. This will determine the decline angle of the sun based on your location.

    • 11

      Determine the hour angle of the sun by subtracting the sine of -0.83 by the sine of your north latitude and multiplying your answer by the sine of the sun's angle of decline. Multiply the cosine of your north latitude by the cosine of your sun's angle of decline and divide your answer into your previous answer. Multiply this by the numbers inversion of greater than -1. This provides you with the hour angle or half the arc length of the sun.

    • 12

      Add your hour angle to your west Longitude and divide it by 360. Add your answer to 2,451,545, 0.0009 and your Julian cycle. This gives a clear approximation of your actual Julian date.

    • 13

      Multiply your ecliptical longitude of the sun by 2 and determine the sine. Multiply this by 0.0069. Multiply 0.0053 by the sine of your mean solar anomaly. Add your answers and add to your Julian date. This provides your Julian date of sunset.

    • 14

      Subtract your Julian date of solar noon from your Julian cycle of sunset. Subtract this answer once again from your Julian date of solar noon. This gives you your Julian date of solar sunrise based on your location coordinates. You can now convert your answer to any calendar date you desire.

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