Hello Brian, Thank you for the quick reply. I have imaged TX Cnc over a couple of night and should have a full curve in the 3 colors. I'm taking data for a professor who wanted it in the three colors. I looked at some papers and found only UBV values for reference stars HD 1395 1070. How do I know if Simbad data is 'real' photoelectric or CCD ? I have not looked at the site you refered me to, but I will as soon as I have some time. Thanks. Arno van Werven