Radius of icy moons around different late-type stars with a given MO depth. The moon’s geometric albedo was set to A_g = 0.84 in each case (according to the reflectance of ice in the J photometric band), and the distance from the star is at the snowline, that is calculated from Eq. (16), and indicated in the top axis, too. Green and light blue coloured curves indicate the estimated photon noise levels with 5σ confidence of HST and E-ELT, respectively. Orange and red curves depict the same for JWST but with two different filters (F140N and F115W, respectively). Grey vertical lines indicate the 60, 90 and 120 min MO duration contours for a moon in circular orbit around a Neptune-mass planet.