Below, the interactive procedure will be described first, simply because it is easier. Definitely, it is not recommended to follow this procedure for photometry on more than 100 stars. However, a certain degree of interactivity has the advantage that it makes the user aware of what he/she asks the computer to do and he/she shares with it responsibility for the results.
Of course, to start interactive photometry of program stars one should select the stars. This can be done with the command: