How are cepheid variables used to determine distances to nearby star clusters??
I understand that you have to find some cepheids whose distances are already known from a nearby galaxy. Then work out the luminosity (using observed brightness) and periods and plot them in a graph (linear relationship: longer period means greater luminosity).
Then find a cepheid in another galaxy of interest. Measure the period of the cepheid and its observed brightness. Then you read off the luminosity from the previous established graph that showed the linear relationship.
What do you do after this?
add point: How is observed brightness worked out?