Defect of Illumination
Defect of illumination is the maximum angular width of the unilluminated part of a celestial body seen by a given observer. For example, if an object is 40 seconds of arc across and is 75 percent illuminated, the defect of illumination is 10 seconds of arc.
Read more about this topic: Angular Diameter
Famous quotes containing the words defect and/or illumination:
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