The name translates as "goat-horned star plant".
There are several species of Astrophytum. They are beginners'cacti but I have neglected them for many years, only recently adding some to my collection.
I have made some adjustments to the colour of some images.
The stereos are crosseye.
Olympus EM-1, (aperture priority), Olympus 4/3 50mm f2 macro, f11, f13 or f14 ISO 250, hand-held.