I don't think I would intentionally even leave Catts, Phals and some Onc. as low as 50 but it is likely OK. I run the greenhouse in winter at 55F nighttime temp and a large variety of chids are fine with that. I do have a heat mat for several warm loving Catts and Dens tho.

When they are kept cool, remember not to over water.

going down to 0 tonight so everyone is in. My catts are so young they only went out for partial days when it was optimal, same with the oncidium and baby Vanilla but they were never out nights even in august. Ill probably set my cyms back out tomorrow for the day but going to have to watch the weather

Everything has already been said, but large standard cymbidiums can take quite a bit of cold so you can leave it outside until first frost.

How is your phal?? I hope it is fine.
6 C is way too cold for it. I would not expose them to anything under 15 C. I had a terrible experience with phals as a kid. I learned the hard way. lol

Certain cattleyas can also take quite a bit of cold, but just to be sure, keep it above 10 or 15 for good health. Most cattleyas I believe almost all, respond to day length to know when to flower, and some need "drier" period like walkeriana.

Good to know about the Catt's flowering requirements mine are all small and live on a seedling heat mat. my phals are noId and in the winter the heat is set at 15 so its never colder then that, but my place is generally on the cool side, the phals look fine they definitely didn't freeze they are probably in for the season now... hoping the one with the little nub of a spike wakes up soon and gets to flowering. The cyms are back out for the day at least not sure how tonight will be.

good that your phals are fine. If they show spikes, do not suddenly move them to a different locations where the temperature is quite different.
Since yours place is on the cooler side, I don't think it'll be a much of a problem.

If you are keeping it at around 15C day and night, then you might want to be careful with watering.

Also, if your place gets lots of light during the day, there will still be enough diurnal difference.
At 15C, I would feel quite chilly and need a warm jacket on.

Remember phals in general will spike just fine in warmer conditions. It's the general decline of the temperature that signals them to set spikes rather than a certain set temperature.
After hot summer, just a slight drop of indoor temperature is enough to help them spike.
say, night minimum 18 C give or take.