I agree with the translation by Gunella (ciao Magun!) (expecially the first; the second one is not clear to me... I am not a latinist!)
If the subject who rescues or saves is the sundial, I suggest "occulta servo" or, since "occultus" is a little ambiguous, "invisibilia servo", even if "invisibilis" is quite rare. Regards. Giuseppe Viara
