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Re: [AAVSO-DIS] Why Aren't Arne's Sequences Solid Gold? > So, to cut to the quick, if someone were to write a paper and transform > their magnitudes using Henden sequences and state something like > "transformed to the Johnson/Cousins system using Henden sequences of the > field", would this be inaccurate? i.e. Henden != Johnson/Cousins? Or is > the fact that the fictional data in question is related to Henden and > Henden is related to Johnson/Cousins going to become acceptable? If the passbands of your CCD + filter (+telescope, atmosphere etc.) is closer to those of the Johnson/Cousins than those of Henden's, and you are specially in pursuit of getting as much standard systems as possible, you would be better to stick to the original Johnson/Cousins standard stars. Otherwise, I don't see a practical reason not to use the Henden sequences to their limit of accuracy and consistency. In practical photometry, the use of these "field sequences" is usually adequate. However, one should bear in mind that these field sequences of an arbitrarily chosen area does not contain a neccesary spread of stellar colors to calibrate the color term (the well-known field of M67 is not sufficient in this point of view), or can be suffered from a considerable degree of reddening, which would introduce additional transformation errors. If you are trying to calibrate your system covering a wide range of colors, you may consider all-sky photometry using the Johnson/Cousins standard stars. > The closer you (in complexity of the transformation) can make the > measurement to the accepted standard, then the easier it will be for > someone to accept it. Complexity of the transformation is not always a good indicator of the better approximation of the standard system. Even with any degree of complexity, one can not make transformations between systems with very different passbands. In attempting to make standard photometry, design as close passbands as possible as the originally defined ones, rather than to numerically transform measurements. Regards, Taichi Kato
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