Comments on one aspect of J.Percy's paper
I applaud Percy's recent paper that encourages continuing visual observations. As many older members appreciate, there has been no bigger supporter of the AAVSO's visual program over the past several decades than myself. However, one has to use caution in what they are encouraging among observers, lest the true purpose of the observer's motivations go off in the wrong direction.
My case in point concerns a passage in Percy's paper addressing the observation of nebula variables, where he states:
"Back in the 1970's, some AAVSO visual observers began observing these stars. They tend to occur in specific star-forming regions, so they can be observed very efficiently. The observers were able to make many thousand observations of them each year, and thus rank high on the list of top observers. Finally, Director Janet Mattei declared that visual observations of T Tau stars [meaning specifically the Orion Nebula variables] would be devalued by a factor of ten in the annual observer totals. The observations languished, unvalidated."
While Percy and his students would seem to have derived some apparent value from these data after encouraging the Director to validate a portion of them, I would say that one must be very cautious in drawing any conclusions from these data.
Back in the 1970's I participated in the nightly observations of these stars. It was soon recognized that a number of the comparisons stars themselves were variable and the remainder on the charts really were not very good at all. Compounding these problems was the fact that in many instances while the comparison stars were seen on a relatively dark sky background, the variables were viewed against a much brighter nebula veil. That situation, alone, renders truly accurate magnitude estimates highly questionable, if not outright impossible, especially to small fractions of a magnitude. As a result, I soon dropped my observation of these stars to concentrate of more worthwhile stars.
I would also have to perhaps question the motivation of several of the observers of the time who were making brightness estimates every ten minutes or so over the course of hours. This resulted in thousands of observations likely made more for the purpose of generating numbers than a real desire to gather scientifically valid data. Director Mattei also recognized this and after a time curtailed the tallying method with regard to observer totals. I would further point out that when this situation came about most of the prolific nebula variable observers dropped their monitoring programs, to my mind clearly indicating what their actual motivation was.
What is always needed in AAVSO programs is a certain degree of oversight and feedback that keeps observers on the straight and narrow. Over the course of the three decades I edited the AAVSO Circular I saw a number of otherwise promising observers redirect their observing programs specifically to the purpose of generating ever greater numbers, rather than useful data. The situation is still with us today, and is seen in some of today's prolific observers making nightly observations of bright Mira stars, something that serves only to skew the final combined data.
I have long felt that far greater AAVSO emphasis needs to be placed on at what intervals various types of variables should be observed. Excessive observation of slowly varying stars, especially when specifically done for the purpose of generating numbers, needs to be curtailed as it is harmful in several ways. I know that in the era of Director Margaret Mayall such guidelines were set on submitting observations. Those data that violated the rules was dropped. Perhaps such stringent policing might not be a bad idea still today.