Calculating errors

Hi All,

Sorry if this question is a bit simple but I want to check that my calculation of comp star errors is sound. SeqPlot provides the V magnitude and B-V color index of potential comp stars. The error of each is also reported, i.e.:

V = 5.000, error = 0.010 and B-V = 0.500, error = 0.015

So the B magnitude is V + (B-V) = 5.500, simple enough. But errors should be added in quadrature:

B error = SQRT(0.010*0.010 + 0.015*0.015) = 0.018

Is this correct? Cheers,

Mark