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Hi, Mike, > Respectfully, my problem with Sebastian reporting visual estimates to 0.01V > has always been with the uncertainties of the comparison stars used to make > the estimates. Very few photometrists would claim this degree of accuracy, > even under ideal conditions. I don't claim that accuracy. I know generally I am in the 0.05 magg. level. But this is always a whole lot better than reporting to 0.1 mag. Anyway I do it only for selected naked eye stars, but certainly all observations would be better represented (not as steps in a ladder) if reported to two decimal places. The point is that it makes no sense for a hundred of people database. If not, the difference in recording observations to one or two decimal places is huge. regarding the comparison stars, I work with brighter stars and the magnitudes are pretty good. > Naked eye or binocular observations from a balcony within city limits > certainly do not qualify as ideal conditions. Now mix in direct vision, > averted vision, color of comp stars according to imperfect datasets, weather > and observer physical variables, and you have a real bitches brew of > uncertainty. Not as much as it seems from your words, Mike. Polluted Bs As skies have never been a problem for me, on the contrary, a little brightness in the background induces a slower transition between cone and rod vision and it helps me a lot. I really get in trouble when I go out to the dark country skies. I actually end up doing deep sky observing instead of variables!!!!! And the mix of types of vision is to get better results so please, don't include it in your list of "problems" when they have been my "solutions"! ;-)) Apart from that, of course there is an intirinsic error in visual observations and it would be silly to deny it. It's just that useful information is hidden in some cases by the current reporting method. Another thing that it is very important, is the difference between observations made with different instruments. With the naked eye I am generally at 0.05 mag. With binoculars between 0.05 and 0.1 but with a telescope, generally between 0.1 and 0.15. Since most of you work that way, I think our differences about accuracy have more to do with this than with some special skills some of us could have. If you get 0.1 mag. accuracy with a telescope, that is real good for me~! > Magnitudes reported are never 2.63 +/- 0.05, they are 2.63 Otero "human > photometer" V. > I don't doubt that variations of 0.05V can be seen by visual observers > observing events in human timescales like EB eclipses. But night to night > variations of this amplitude reported by visual observers, or the majority > of CCD observers is suspect at best. Most amateur observers just don't have > the conditions or tools to do it at this level. > > There are some really talented people doing TASS photometry, and they can't > do better than 0.03V after a few years of trying. ASAS3 data is reliable to > some degree to around 11.5V, but it is not the answer to southern all sky > photometry even to 13V. > > I think most serious people agree mv transformations were a bad idea, based > on a faulty assumption. The BAAVSS is revising their charts based on this > system to more accurately reflect Johnson V. AAVSO has embarked on a path > towards the same goal. The main advantage here will be commingling visual > and CCD observations down the road. I have my doubts about trying to > transform historical AAVSO v mag estimates to Johnson V, because of the > incoherent state of the comp stars used in many cases. > > This does not in any way lessen the degree of usefulness of the data. It > just means that there will be a "hiccup' in the data some day that will show > up when observations are based on a standard system. Eventually, the new > observations will outnumber the historical data, and this hiccup will be of > little consequence. > > The bottom line is, whether you make visual or CCD observations you need to > exercise care and discretion in all you do to report the best estimate of > the magnitudes of the stars you observe. Let the people who analyze the data > make decisions about the accuracy and usefulness based on their needs and > expectations. > > For those of you who are just getting started, do not despair. This _is_ > actually fun to do, and your contributions are important. > > Visual observers armed with good sequences can make estimates accurate to > 0.1V and CCD observers should be able to match or better this accuracy given > time and training. Practice makes perfect. > > Reminds me of our senior football squad. At the beginning of the season we > couldn't run off tackle to the right against the cheerleaders and make > positive yardage. By the time the conference championship rolled around we > were knocking the snot out of our opponents for long yardage using two or > three plays to the right. > > We're all in this together. Go team! In short, I think we are all way better than a couple of years ago. And it will surely be getting better. Cheers, Sebastian.
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