File:Twilight illumination by sun altitude luxes 2 r 1.svg

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Captions

Captions

Illumination of twilight by sun altitude degrees

Summary

[edit]
Description
English: Illumination of twilight by sun altitude degrees
Date
Source Own work
Author Merikanto

Python source code

based on data from R "moonlit" package

https://github.com/msmielak/moonlit

Original source of data

        2. Twilight illumination from empirical data https://www.jstor.org/stable/44612241
        1. Sun Position and Twilight Times for Driver Visibility Assessment; Duane D.
        2. MacInnis, Peter B. Williamson and Geoffrey P. Nielsen; SAE Transactions;
        3. Vol. 104, Section 6: JOURNAL OF PASSENGER CARS: Part 1 (1995), pp. 759-783
        1. Values calulated from the paper for angles -18 to 5 degrees, by 0.25 degree, imported to R and spline function applied

Python3 polyfit code

    1. illumination of twilight
    2. python3 source code
    4. 19.8.2023 0000.0000

import math import numpy as np import matplotlib.pyplot as plt

    2. uses data from
    4. https://github.com/msmielak/moonlit
        2. Twilight illumination from empirical data https://www.jstor.org/stable/44612241
        1. Sun Position and Twilight Times for Driver Visibility Assessment; Duane D.
        2. MacInnis, Peter B. Williamson and Geoffrey P. Nielsen; SAE Transactions;
        3. Vol. 104, Section 6: JOURNAL OF PASSENGER CARS: Part 1 (1995), pp. 759-783
        1. Values calulated from the paper for angles -18 to 5 degrees, by 0.25 degree, imported to R and spline function applied

sun_altitudes0=np.array([5,4.75,4.5,4.25,4,3.75,3.5,3.25,3,2.75,2.5,2.25,2,1.75,1.5,1.25,1,0.75,0.5,0.25,0,-0.25,-0.5,-0.75,-1,-1.25,-1.5,-1.75,-2,-2.25,-2.5,-2.75,-3,-3.25,-3.5,-3.75,-4,-4.25,-4.5,-4.75,-5,-5.25,-5.5,-5.75,-6,-6.25,-6.5,-6.75,-7,-7.25,-7.5,-7.75,-8,-8.25,-8.5,-8.75,-9,-9.25,-9.5,-9.75,-10,-10.25,-10.5,-10.75,-11,-11.25,-11.5,-11.75,-12,-12.25,-12.5,-12.75,-13,-13.25,-13.5,-13.75,-14,-14.25,-14.5,-14.75,-15,-15.25,-15.5,-15.75,-16,-16.25,-16.5,-16.75,-17,-17.25,-17.5,-17.75,-18]) sun_illuminations0=np.array([4499.368645,4251.166227,4010.398231,3776.215801,3547.994929,3325.316934,3107.949504,2895.827638,2689.034018,2487.778469,2292.376367,2103.225979,1920.784922,1745.546056,1578.01326,1418.677674,1267.99505,1126.364901,994.1121318,871.4718063,758.577575,655.4541802,562.0142693,478.0595544,404.556034,338.5269901,281.0455199,231.5470057,189.3612856,153.7599131,123.995336,99.33178815,79.06826738,62.55436811,49.1999767,38.47993901,29.93480689,23.16869331,17.84514167,13.68176809,10.44428227,7.911259933,5.993606008,4.527348005,3.411591605,2.566090598,1.927671576,1.447053311,1.086102387,0.815522737,0.612949604,0.461403805,0.348056383,0.263253638,0.199755997,0.152149406,0.116393841,0.089479462,0.069166322,0.053788354,0.04210643,0.033198579,0.026378238,0.02113351,0.017082103,0.01393796,0.01148655,0.009566583,0.008056477,0.006931022,0.00596833,0.00519104,0.004556611,0.004033257,0.003596965,0.003229411,0.002916468,0.002647147,0.002412827,0.002206692,0.002023321,0.001858385,0.001708419,0.001570657,0.001442901,0.001323428,0.001210913,0.001104369,0.001003101,0.000906659,0.000814804,0.000727464,0.000644703])

sun_altitudes1=sun_altitudes0[::-1] sun_illuminations1=sun_illuminations0[::-1] log_sun_illuminations2=np.log10(sun_illuminations0[::-1])

fit1=np.polyfit(sun_altitudes1,log_sun_illuminations2,6) poly1=np.poly1d(fit1)

altitudes2=np.linspace(-18,5,230)

  1. altitudes2=np.linspace(-18,90,900+180)

log_illums2=poly1(altitudes2)

  1. print(log_illums2)

fig = plt.figure() ax = fig.gca() ax.set_xticks(np.arange(-21, 6, 3)) ax.set_yticks(np.arange(-4, 4,0.5))

plt.xlabel("Altitude of Sun, degrees", size=18) plt.ylabel("Log10 of illumination lx", size=18)

plt.yticks(fontsize=18) plt.xticks(fontsize=18)

plt.suptitle("Illumination of twilight, luxes", fontsize=22) plt.title("From empirical data", fontsize=18)

  1. plt.plot(alts1, logillums1, linewidth=6, color="#ff7f00")
  2. plt.plot(x2,y2,linewidth=6, color="#ff7f00" )
  1. plt.plot(altitude, log10_lux, linestyle=":", linewidth=4, color="#ffff00")

plt.plot(altitudes2, log_illums2,color="#ff7f00", linewidth=6 ) plt.scatter(sun_altitudes1, log_sun_illuminations2, marker='+', color="red")

plt.grid()

plt.axvline(x = 0, color = '#FFFF00', label = 'Sunset') plt.axvline(x = -6, color = '#7f7f00', label = 'Civil twilight ends') plt.axvline(x = -12, color = '#3f3f00', label = 'Nautical twilight ends') plt.axvline(x = -18, color = '#1f1f00', label = 'Astronomical twilight ends')

plt.text(-5, 0, "Civil twilight", size=17) plt.text(-11.5, -1, "Nautical twilight", size=17) plt.text(-17.5, -2, "Astronomical twi.", size=17)

plt.show()


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