From Dr Apostolos Christou, Armagh Observatory:
A variety of observing methods are suitable for the scientific study of mutual events. CCD and video devices can both be used to carry out these observations.
The objective is to measure the variation with time of the light level of the eclipsee/occultee relative to some nearby reference object eg a star or another satellite - a procedure that is known as relative (or differential) aperture photometry.Key requirements are:
Speed
Speed
Typically one would need to generate a sample per second for a predicted five-minute event. As a rough guideline one should plan his/her observations with a view to acquiring at least 300 and less than 1000 samples (the latter if you are disk-space limited) for a given event.
Reference
The light from the satellite will most probably vary during the event for reason other than the eclipse/ occultation. As the elevation of Jupiter in the sky changes so does the atmospheric extinction of starlight (or, in our case, satellite-light). In addition, changes in atmospheric conditions (haze, high altitude class) exacerbate the problems. For these reasons IT IS IMPERATIVE THAT YOU HAVE A REFERENCE OBJECT IN YOUR FIELD OF VIEW to correct for these effects during the reduction process.
Time
The need for accurate time information is as important as the need for a reference object. The usefulness of any observations is reduced greatly if the individual sample is not somehow time-stamped in an absolute scale (eg UTC) sufficiently accurately. Typically, time accuracy should be 0.2 seconds or better.