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Schröter Effect 2018


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About this observation
David Basey
Time of observation
24/10/2018 - 10:10
358mm Newtonian

During the current Eastern elongation of Venus I have been able to make observations on 22 separate days. In most cases it has been possible to record the planet using three separate filters, W15 (Yellow), W47 (Blue) and W25 (Red).

Part of each observation is to record the apparent phase. The difference between the observed value and the theoretical dictated by purely geometrical concerns is the well known Schröter effect.

As usual, for much of the elongation, the observed phase is less than theoretical. The effect decreases and ultimately reverses as inferior conjunction approaches. If it did not the planet would disappear prior to conjunction!

Notice how:

  1. The phase in blue light is consistently less than in yellow and the blue trend line runs nearly 'parallel' to that for yellow.
  2. The phase in red light starts out smaller than the yellow but at phases less that about 0.7 become greater.
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