Don't call result of your calculations Ksp - Ksp is constant that is characteristic for every substance. You do calculate a value of Ksp formula using known concentrations - and then you compare it with known Ksp. In this case calculated value is 3.58*10

^{-3} (you are OK), it is larger then Ksp for Ca(OH)

_{2} - so the precipitate forms.

In short: you are right this time