Finding the Angular Distance Between Jupiter and its Moons (Galilean)

[Dreyth]

I am having the hardest time figuring out the angular distance between Jupiter and Io, Europa, Ganymede and Callisto!

I asked my teacher for help: "How would one find the angular distances between Jupiter and its
moons?"

and he said: "Do you know the field of view of your telescope? Once you know that,
you can just compare the apparent Jupiter-moon distance to the full
width of the field of view.:

I'm must be just missing something. Can someone help me by either explaining what he meant, or by giving me a somewhat easy (it's late) way of finding it out for myself?

 

[zhermes]

What he's saying is that if you know your entire field of view (FOV) is 1arcmin, and the apparent distance between Jupiter and a moon is half of the FOV, then you know the angle is half an arcmin.

Otherwise, you could find out the true distance between Jupiter and the moon, and use your distance away from Jupiter to calculate the angle.