While every (astro)physical measurement method of course has associated uncertainties as specified in the quoted error, an averaging of many independent determinations will strongly reduce the error from only a single measurement. That's what is done in my galaxies.dsc catalog for Celestia 1.6.0. Of course, Tully-Fischer is part of this. The most accurate method is based on Cepheids.TheShadow1138 wrote:I would also like to address my previous statements concerning the "much more accurate" distance for M33. I did not mean to imply that it is the most scientifically accurate distance as I am well aware that measuring distances to galaxies can yield many varying results depending on the methods used, especially with the possibility that Type Ia supernovae may not have a uniform brightness.