Strange, Iapetus was the second moon of Saturn (after Titan but before Rhea) that I found with my 60 mm refractor more than 40 years ago. I verified Iapetus with The Astronomical Ephemeris (the predecessor of The Astronomical Almanac) and I saw the movement of the moon during consecutive nights. Iapetus is of 10th magnitude in western elongation. I have also seen Iapetus many times with 20x100 binoculars. Himalia was a tough jovian moon with my 10-inch Dob when Jupiter was high up for me 10 years ago.