Re: Calculation of apparent magnitude from apparent brightness

Posted by AstroT on Jul 12, 2024; 12:12pm
URL: http://astroimagej.170.s1.nabble.com/Calculation-of-apparent-magnitude-from-apparent-brightness-tp2475p2477.html

Thank you Karen. I think I got the idea behind differential photometry: ratios in fluxes give differences in magnitudes. But many textbooks introduce magnitude as m = -2.5*log10(F). Is F the summed ADUs (multiplied by the gain; I forgot that detail in my previous email) divided by (texp*A)? Then the unit of F would be electrons per second per squaremeter. However, is it permissible to take the logarithm of a dimensioned quantity? Taking the log. of a ratio of two F's provides a dimensionless quantity and then all is good.