Gennady Tycho is accurate to 0.05 magnitudes for stars brighter than mag 10. But remember that you have to convert the magnitudes. Systematic errors probably drive the error above 0.05 magnitudes.
http://www.projectpluto.com/photomet.htm V = VT - 0.090 * (BT - VT) B - V = 0.850 * (BT - VT) Depending on what you want to do, you might look to either the Landolt standards or the Henden sequences. Neither are especially user friendly. There is a job for someone. Make a catalog of Landolt standards. Henden sequences would be more of a problem since there are a lot of them and more are being added all the time. Jim Jones G. G. wrote: >John, > >Thanks for responding. > >So, which catalogs (accessible through CDC) are photometric catalogs? >Also, if none is, are there good photometric catalogs on-line? > >Thanks, >Gennady > >--- In [email protected], John Mahony ><[EMAIL PROTECTED]> wrote: > > >>These were intended as astrometric catalogs, not photometric. To >> >> >quote from > > >>"read.pht", the readme file on the USNO's website for the >> >> >photometric data in > > >>the USNO-A1.0 catalog: >> >>----------------------------------------- >>Summary: >> >> The photometric calibration of USNO-A1.0 is about as poor as one >> >> >can > > >> have and still claim that the magnitudes mean something. >> ..... >>-------------------------------------- >> >>-John >> >> >> >>--- "G. G." <[EMAIL PROTECTED]> wrote: >> >> >> >>>Often, I use catalogs USNO-A and USNO-B to identify faint stars. >>>However, on many occasions these catalogs do not agree. Often, >>> >>> >the > > >>>difference is quite large (1+ magnitudes). Does anyone know which >>> >>> >of > > >>>these catalogs is more accurate? >>> >>>Thanks, >>>Gennady >>> >>> >> >> >> >> >> >_ > > > > >
