There is nothing special about this Moon image - except that I was able to take it at all. I have just discovered that a feature in the INDI software that defaults to "force Bulb mode" on DSLR cameras is what had been preventing any exposure faster than 1 second in the Ekos camera module. Switched to OFF, now I can shoot something as bright as the Moon. Nikon D750 on Sky-Watcher Explorer 150P, 1/4000th [0.000250 in Ekos] at ISO 800: three exposures, blended in PhotoShop ... and then the clouds rolled across.