[Aavso-photometry] Best options for averaging files.

[Terry Bohlsen]

Dear All
I am new here and would first like to say hello. 
I have commenced taking images for photometry and have been taking reading of long period variables and analysing them with AIP4WIN new mag measuring tool.
I have measured my transformation coefficients on a number of runs as suggested in the Cohen paper and am happy with them.
My question is, what is the best method of combining images taken sequentially?
Currently I take 3-5 exposures through each filter. I then have the option of median combining the images and then measuring the mags on the combined image or I can measure the mags on the individual images and either submitting the individual readings or to average the readings over the 3-5 images and submitting that.
Which is preferred?
Thanks in advance.

Terry Bohlsen
Armidale
NSW
Australia