Hi Nicky,
"One called Red Star" still doesnt help Im afraid, is it a Cattleya, Odontoglossum or some other species?
Well I can tell you now the Miltonia wont last 5 minutes in your south facing exposure, they sunburn very easily even if they are on east facing windows. The best place for them is a few feet away from the window and shaded by some other plants.
Same for the ,Miltionopsis, they are very similar in growing conditions and they even used ot be in the same genus.
Cattleya wont like south facing sun either, they enjoy east facing windows but south facing exposures will just sizzle them.
Odontoglossums wont do well on south facing windows either, again, youre better off with east facing widnows or exposures.
Generally most orchids hate that much sun, except for in the winter when Vanda enjoy being on south facing exposures.
However, it might work if you shade them with shading cloth, but I wouldnt ge my hopes tooo high up about that since Ive never tried it.