I don't have Notocactus, but I regularly bring my orchid cactus and other succulents outside for the summer. I would think it would be okay as long as you remember to harden it off properly as you would any plant that has been in the house using artificial light or sunlight through a window. By that I mean start exposing it only very gradually to sun. I start mine outside in dappled shade and over the course of a week or two get move them gradually to more sun until they can adapt to it.