Thanks Jim. My question arose from my experience with Byzantine Christianity and non-recognition of the crescent + star in that context. Clearly, this symbol and its relatively minor association with Byzantium prior to Christianity, and its strong association with Turkish Byzantium/Istanbul after the conquest in 1453, does not counter by experience. 

Very interesting indeed, especially it relatively late acceptance as a symbol of Islam. I had assumed without evidence that it arose with the spread of Islam from the time of Mohammed. 

Thanks for the education.