Schröter effect

Schröter effect

A discrepancy between the predicted phase of Venus and the one that is actually observed. In particular, the effect relates to the fact that the calculated date of dichotomy does not coincide with the date on which Venus is seen to have a completely straight terminator. Morning dichotomy is usually earlier than predicted, evening dichotomy later. The reason for the effect is unknown; it may be due to observational error or atmospheric distortions. The effect takes its name from the German astronomer Johann Hieronymus Schröter (1748–1816), who noted it in the 1790s.

Schroter effect

[′shrōd·ər i‚fekt]
(astronomy)
The occurrence of the dichotomy of Venus earlier than theoretically predicted when it is waning, and later than theoretically predicted when waxing.