Abstract

The recording spectroradiometer for collecting data on the spectral distribution of daylight at Delhi is briefly described. The chromaticities calculated on the 1931 CIE system from 187 spectral curves, recorded over about a year, are presented and their distribution about the Planckian locus is discussed. The typical spectral distributions for the correlated color temperatures 4800, 5500, 6500, 7500, and 10 000°K, derived from the characteristic vectors are presented and discussed.

© 1968 Optical Society of America

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References

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  1. D. B. Judd, D. L. MacAdam, and G. Wyszecki, J. Opt. Soc. Am. 54, 1031 (1964).
    [Crossref]
  2. S. T. Henderson and D. Hodgkiss, Brit. J. Appl. Phys. 14, 125 (1963).
    [Crossref]
  3. G. T. Winch, M. C. Boshoff, C. J. Kok, and A. G. du Toit, J. Opt. Soc. Am. 56, 456 (1966).
    [Crossref]
  4. S. R. Das and V. D. P. Sastri, J. Opt. Soc. Am. 55, 319 (1965).
    [Crossref]
  5. V. D. P. Sastri and S. R. Das, J. Opt. Soc. Am. 56, 829 (1966).
    [Crossref]
  6. J. L. Simonds, J. Opt. Soc. Am. 53, 968 (1963).
    [Crossref]
  7. R. Stair and R. G. Johnston, J. Res. Natl. Bur. Std. (U. S.) 57, 205 (1956).
    [Crossref]
  8. H. R. Condit and F. Grum, J. Opt. Soc. Am. 54, 937 (1964).
    [Crossref]
  9. K. L. Kelly, J. Opt. Soc. Am. 53, 999 (1963).
    [Crossref]
  10. Y. Nayatani and G. Wyszecki, J. Opt. Soc. Am. 53, 626 (1963).
    [Crossref]
  11. R. V. Karandikar, Proc. Indian Acad. Sci. 28A, 46 (1948).
  12. D. Nickerson, J. Opt. Soc. Am. 50, 90 (1960).
    [Crossref]
  13. G. Wyszecki, personal communication.
  14. S. T. Henderson and D. Hodgkiss, Brit. J. Appl. Phys. 15, 947 (1964).
    [Crossref]
  15. M. P. Thekaekara, Solar Energy 9, 7 (1965).
    [Crossref]
  16. F. W. Paul Götz and E. Schönmann, Helv. Phys. Acta 21, 151 (1948).

1966 (2)

1965 (2)

1964 (3)

1963 (4)

1960 (1)

1956 (1)

R. Stair and R. G. Johnston, J. Res. Natl. Bur. Std. (U. S.) 57, 205 (1956).
[Crossref]

1948 (2)

F. W. Paul Götz and E. Schönmann, Helv. Phys. Acta 21, 151 (1948).

R. V. Karandikar, Proc. Indian Acad. Sci. 28A, 46 (1948).

Boshoff, M. C.

Condit, H. R.

Das, S. R.

du Toit, A. G.

Grum, F.

Henderson, S. T.

S. T. Henderson and D. Hodgkiss, Brit. J. Appl. Phys. 15, 947 (1964).
[Crossref]

S. T. Henderson and D. Hodgkiss, Brit. J. Appl. Phys. 14, 125 (1963).
[Crossref]

Hodgkiss, D.

S. T. Henderson and D. Hodgkiss, Brit. J. Appl. Phys. 15, 947 (1964).
[Crossref]

S. T. Henderson and D. Hodgkiss, Brit. J. Appl. Phys. 14, 125 (1963).
[Crossref]

Johnston, R. G.

R. Stair and R. G. Johnston, J. Res. Natl. Bur. Std. (U. S.) 57, 205 (1956).
[Crossref]

Judd, D. B.

Karandikar, R. V.

R. V. Karandikar, Proc. Indian Acad. Sci. 28A, 46 (1948).

Kelly, K. L.

Kok, C. J.

MacAdam, D. L.

Nayatani, Y.

Nickerson, D.

Paul Götz, F. W.

F. W. Paul Götz and E. Schönmann, Helv. Phys. Acta 21, 151 (1948).

Sastri, V. D. P.

Schönmann, E.

F. W. Paul Götz and E. Schönmann, Helv. Phys. Acta 21, 151 (1948).

Simonds, J. L.

Stair, R.

R. Stair and R. G. Johnston, J. Res. Natl. Bur. Std. (U. S.) 57, 205 (1956).
[Crossref]

Thekaekara, M. P.

M. P. Thekaekara, Solar Energy 9, 7 (1965).
[Crossref]

Winch, G. T.

Wyszecki, G.

Brit. J. Appl. Phys. (2)

S. T. Henderson and D. Hodgkiss, Brit. J. Appl. Phys. 14, 125 (1963).
[Crossref]

S. T. Henderson and D. Hodgkiss, Brit. J. Appl. Phys. 15, 947 (1964).
[Crossref]

Helv. Phys. Acta (1)

F. W. Paul Götz and E. Schönmann, Helv. Phys. Acta 21, 151 (1948).

J. Opt. Soc. Am. (9)

J. Res. Natl. Bur. Std. (U. S.) (1)

R. Stair and R. G. Johnston, J. Res. Natl. Bur. Std. (U. S.) 57, 205 (1956).
[Crossref]

Proc. Indian Acad. Sci. (1)

R. V. Karandikar, Proc. Indian Acad. Sci. 28A, 46 (1948).

Solar Energy (1)

M. P. Thekaekara, Solar Energy 9, 7 (1965).
[Crossref]

Other (1)

G. Wyszecki, personal communication.

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Figures (14)

Fig. 1
Fig. 1

Chromaticities of daylight at Delhi along with the Planckian, Judd–MacAdam–Wyszecki and Abbot–Gibson loci.

Fig. 2
Fig. 2

Loci of the chromaticities of daylight obtained for different places along with the Planckian locus. A: Planckian, B: Abbot–Gibson, C: Judd–MacAdam–Wyszecki, D: Pretoria, E: Henderson and Hodgkiss, F: Delhi.

Fig. 3
Fig. 3

Characteristic vectors V1 and V2 derived from the Delhi data.

Fig. 4
Fig. 4

Typical spectral distributions of daylight at Delhi for correlated color temperatures: 4800, 5500, 6500, 7500, and 10 000°K reconstituted from the mean and the first two characteristic vectors. Wavelength in nm.

Fig. 5
Fig. 5

Comparison of computer-derived (continuous line) and measured (shown by the points) distributions for 4800°K. Wavelength in nm.

Fig. 6
Fig. 6

Comparison of computer-derived (continuous line), average-derived (discontinuous line), and measured (shown by the points) distributions for 5500°K. Wavelength in nm. x and y for the average-derived distribution are 0.3298 and 0.3355.

Fig. 7
Fig. 7

Comparison of computer-derived (continuous line), average-derived (discontinuous line), and measured (shown by the points) distributions for 6500°K. Wavelength in nm. x and y for the average-derived distribution are 0.3113 and 0.3199.

Fig. 8
Fig. 8

Comparison of computer-derived (continuous line), average-derived (discontinuous line), and measured (shown by the points) distributions for 7500°K. Wavelength in nm. x and y for the average-derived distribution are 0.3007 and 0.3108.

Fig. 9
Fig. 9

Comparison of computer-derived (continuous line), average-derived (discontinuous line), and measured (shown by the points) distributions for 10 000°K. Wavelength in nm. x and y for the average-derived distribution are 0.2789 and 0.2931.

Fig. 10
Fig. 10

Comparison of the typical distribution of Delhi (continuous line) and of JMW (line through open circles) for 4800°K. Wavelength in nm.

Fig. 11
Fig. 11

Comparison of the typical distribution of Delhi (continuous line), of JMW (line through open circles), and of Pretoria (discontinuous line) for 5500°K. Wavelength in nm.

Fig. 12
Fig. 12

Comparison of the typical distributions of Delhi (continuous line), of JMW (line through open circles), and of Pretoria (discontinuous line) for 6500°K. Wavelength in nm.

Fig. 13
Fig. 13

Comparison of the typical distributions of Delhi (continuous line), of JMW (line through open circles), and of Pretoria (discontinuous line) for 7500°K. Wavelength in nm.

Fig. 14
Fig. 14

Comparison of the typical distributions of Delhi (continuous line) and of JMW (line through open circles) for 10 000°K. Wavelength in nm.

Tables (4)

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Table II Mean and first four characteristic vectors.

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Table III Chromaticity coordinates (x,y) of typical daylight for various correlated color temperautres.

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Table IV Scalar multiples of the first two characteristic vectors.

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Table V Relative spectral irradiance of typical daylight of JMW, Pretoria, and Delhi.

Equations (2)

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E λ = Ē λ + M 1 V 1 + M 2 V 2
E λ = Ē λ + M 1 V 1 + M 2 V 2 .