Setting an axis to measure distance from

[aseraucse]

Hello!

I am currently studying (essentially) the movement of a particle when a laser is shone next to it.  I'm very new to imagej so please forgive my ignorance.  I'm trying to set an optical axis in the center of the laser which I am going to define as the point with the highest gray value.  essentially what I need to figure out is how to draw a line which is the fit of the highest intensity points in my image and then measure the movement of a particle near that axis in two dimensions.  any ideas on how I might do this?

Thanks,

Andy Seracuse