I don't have your scope, but I do have a 120 ED doublet f7.5 doublet, metal lens cell.
I have not done a formal test of course, but I do notice some softness of view
when I take the scope out from 68F house to 30F outside. 100x works well,
I notice the softness when exceeding that. Sometimes I go back inside, or
I switch to another low power target. It seems about 30 mintues before the
scope is sharp at 150 to 200x. Nights of 200x seeing are extreemly rare.