This is one of the prettiest of the epiphytic cacti flowers and it is a species, not a hybrid like most others.
I was given a cutting over 40 years ago as "Apple Blossom" but the plant has subsequently been lost. It has taken me several years to find a replacement.
This is its first flower. Mature plants have flowers along both edges of the leaf-like stem.
Olympus EM-1, (aperture priority), Olympus 4/3 50mm f2 macro, 1/160 at f11 ISO 800, hand-held.
The stereos are crosseye.