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Re: [AAVSO-DIS] Reporting observations: Multi-letter codes > For blue stars, incl CVs, the effective wavelength of this observing > window of most CCD cameras is near that of the R band. Therefore R > magnitudes of reference stars (with non-red colours) in the field can be > used. Such observations are usually reported as CR. > If this is applied to yellow-orange stars (G-K) one will end up with a > waveband close to I. I magnitudes of similarly coloured reference stars > could be used for them. Observations are reported as CI. Please don't be confused. For most of stars with usual colors, the effective wavelengths of the most CCDs have close to that of Rc. Effective wavelengths are integrated quntities, and little vary around the mean wavelengths of the original CCD/filter passbands. Your explanation only applies to extremely red objects which virtually emit no light shorter than 650 nm. Regards, Taichi Kato
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