Growing Cattleya outside?

[moniluhum]

My cattleya has been doing extremely well under artificial lights for the winter. It has been growing new shoots through out the season. The weather now is warming with the lows in the mid 50's and the highs in the mid 70's. I've read that Catts do well outside. What would be the best time to transfer. I have a very small greenhouse which allows for sheltered pm nights. Can any one off some ideas.