I just plotted the spectral curve for ES_Sunlight (filtered sunlight) 
from espd_lightsys.inc and compared it to figure 3 at:
   https://www.newport.com/t/introduction-to-solar-radiation

The curves are similar in shape, but the Lightsys curve is higher in the 
red region, while the Newport curve is highest in the blue and green 
regions.  What would account for the difference?

Newport.com's curve is for the Sun at zenith.  What was Pedro Aphalo's 
source?  Could Pedro's curve have been measured with the Sun at a lower 
angle?

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