scatter in observations vs true variability

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Tracie Heywood

Hi Paul, I have no doubt that beginners will “see” delta Cephei change in brightness. The question is whether these changes match the brightness variations of delta Cephei or whether they primarily reflect the largish scatter that is common in newcomers to visual observing. The UK weather is such that it is unusual for there to be 5 or more clear nights in a row. Hence observers are unlikely to follow delta Cephei through a single cycle of variation and instead will have a collection of adhoc observations spread over a period of time. I know from my early experience that converting such sets of observations into a single light curve can produce somewhat disappointing results, with many observations straying a long way from the (hoped for) neat light curve. The 2017 light curve that I included in my previous reply was, in contrast, primarily based on observations by SPA VSS members with many years experience.

Tracie (based in Leek, Staffs, not north Wales!)