Re: [vsnet-chat 1259] Re: H/T chart vs. VT mags... Fraser Farrell wrote: > My guess would be light pollution. I have noticed on many occasions how > a starfield being observed will suddenly change character when my local > football club finally turns off its floodlights! There is a similar > (but slower) effect when the Moon rises or sets. Another possibility may be, as pointed out elsewhere, attenuation of blue light in Japanese atompshere. There is a reported tendency that Japanese observer(s) tend to report fainter magnitude for southern blue stars (CVs). I have confirmed the observer used (probably the same) V magnitudes, and not GSC. The atmosphere (as well as weather ;_;) over Japan seems to be only too incoorperative. > Perhaps the equation should read : > (visual mag) = V + 0.2(B-V) + (streetlight density factor) ? ;-) Perhaps the light polution term will be (visual mag) = V + k(B-V) where k = 0.2 - (streetlight density factor) - (atmospheric attenuation factor) - ... From my observing site (kyoto), k looks close to zero in moonless nights. From super-urban sites (like Tokyo), k seems to be even negative... > > I have heard comet observers use VT rather than V. I would love to hear > > comments from them also. > > I know that Bill Bradfield uses V mags (from a variety of printed > sources), because he doesn't have access to VT mags (or a computer). > Justin Tilbrook works from the closest variable star sequence (usually V > or SPv from VSS RASNZ). I still use V to maintain consistency with my > historical estimates. I have heard the ICQ has recommended (if I understand corrently from indirect information) VT rather than V. I hope this will not lead to further inconsistencies between variable star and comet observers. Regards, Taichi Kato