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Re: [AAVSO-DIS] Bias errors and R CrB > Yes, the announcement of a dimming can bias observers to "see" a variable > fainter than it actually is when the announcement is in fact mistaken. But > an equally common error is that made by observers who continue to estimate a > star like R CrB at maximum after a real dimming has begun -- force of habit, > they don't see the change. Yes, this is a very frequent variety of observer's bias. Further examples of habits include: (1) Some observers reported fainter and fainter as the R CrB-type fade was ongoing, and the observer's reported rate of fading was invariable even after the object reached minimum. A similar thing happens in fading novae. I formerly noticed that a nova was plotted on some variable star chart. The nova had a close (likely unresolvable) companion, which was not marked on the chart. The reported observations indicated a steady fade even below the companion's magnitude. In another case, the object and companion were reversely plotted. The reported observations also indicated a steady fade, and the observer did not notice the error in the chart. (2) Some observers (apparently) reported expected brightness of certain dwarf novae. The difference from the reality becomes biggest when there is an unexpected observation gap -- the object had already faded but the observer apparently reported what is expected. (3) Some observers possibly avoided reporting observations around the times of expected/reported outbursts or declines; either knowingly or unknowingly, the expectations of type 2 become most uncertain around these phases. These habits were common pitfalls what I recognized from an analysis of variable star observations (not necesarily referring to solely AAVSO or VSNET observations). Note that these habits do not apply to all observers. Some observers are marvellously faithful to what they see, but some are unfortunately not as faithful. This tendency does not seem to be particularly related to the observer's degree of experience. Regards, Taichi Kato
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