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Re: V is V, and filters or not > This is completely correct: "V" is "V" and doesn't depend on what > detector you are using. In defense of the AAVSO, I think the main > reason for separating CCDV from PEPV is for observer awards and has > nothing to do with the science. Perhaps there is a better way to do this. > We often do just that in the campaigns that I have been involved with > (especially GRBs). If there is standard photometry available that > covers the same timeframe as an unfiltered amateur observation, that > unfiltered observation is usually dropped since we do not know how > the observation was made nor can we transform it without further information, > usually not worth the trouble. If we know the amateur in question and > have confidence in his/her ability, we will sometimes make contact > and figure it out. However, we usually (and probably unjustifiable) > assume someone who is using standard filters knows a bit more about > photometry and use their data first. I almost completely agree with the statements above by Brian Skiff. Whether unfiltered CCD observations are useful or not strongly depend on the experience, knowledge, and proper analysis of the observer (or data analyst), and on the objects and scientific aims. Random (or sporadic) unfiltered observations by poorly trained observers are frequently useless, or can be even misleading. In practice, unfiltered CCD observations require more skills (than in standard V-band observations) and more knowledge at the observer's side. This needs to be addressed when encouraging unfiltered CCD observations. But unfiltered photometry in certain subjects are not useless as one might think from Arne Henden's message. An excellent example how unfiltered photometry would work can be found in our recent Nature paper on GRB 030329. With known ranges of spectral indices, the CCD response, and the lack of strong spectroscopic lines, one can reasonably use "well-tuned" unfiltered CCD photometry to deduce other important physical parameters. This burst was bright enough to be observed with filters, but the preferred decision at that time was to avoid loss of time and internal inconsistency arising from different instrumental setup. The same (in scientific return) is usually, but not always, true for observations cataclysmic variables depending on the science one wishs to follow. > Here I disagree. There are uses for unfiltered or even non-standard filtered > measures, such as time-of-minimum for eclipsing binaries, superhump > observations of CVs, etc. What is needed is a clear set of instructions > as to how to report those observations. And how to analyze those observations, and what kinds of objects are the preferred targets of this method. > Reporting errors occur for any organization. It is inadequate to refer to them as "errors", whatever intention this sentence would be... Speaking of errors, [from Henden's message] > The differences in reporting and vetting of datasets in vsnet and > AAVSO seem to arise mainly from what you might call cultural differences. > The problems with amateur observers (notably CCD'ers) having a poor or just > incorrect understanding of formal photometric systems has its cause not > in how things are reported by the different groups, ... There is no doubt that a system producing less errors is a better system. Resorting to tradition is not always a better solution. This is clearly the direction what the AAVSO charts revisions are aiming at. The same initiative can be taken with the reporting system of photometric systems. This must be a much less effort than in revising a huge number of charts. My suggestion would be: replace > CCDB Charge-coupled device (blue filter) > CCDI Charge-coupled device (infrared filter) > CCDO Charge-coupled device (orange filter) > CCDR Charge-coupled device (red filter) > CCDV Charge-coupled device (visual filter) by B(CCD) Charge-coupled device (filtered, B-band) Ic(CCD) Charge-coupled device (filtered, Ic-band) Rc(CCD) Charge-coupled device (filtered, Rc-band) V(CCD) Charge-coupled device (filtered, V-band) and omit CCDO. (CCD) is not logically necessary, but will not be specially harmful. Ic instead of I (Rc instead of R) is to avoid confusion with "Johnson" R and I systems -- unmistakable definition is a better definition. Proper instructions such as "what do V-band or B-band mean?", "is my filter a V-band one?" or "what magnitudes should be used for comparison stars?" can be summarized as FAQs, and people are requested to assimilate these matters before actual reporting (ideally before actual observation). What a constructive suggestion! :) Regards, Taichi Kato
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