Is it okay for cattleyas to be outside at 50-60F at night?

[Roberta]

If you want to get a sense of which Cattleya species are cold-tolerant (and so impart that characteristic to their hybrids) take a look at my website. In the "Index of plants" I indicate which ones I grow outside (so they tolerate night temps down to 40 deg F and occasionally get a few hours even lower).