Really nice pic - and the bloom is off of a rather small A. sesquipedale. I have read that there are two varieties of this, one huge variety and a smaller variety.
For those who don't know, this is the orchid that Darwin found and theorized that there had to be a pollinator with a very long tongue / proboscis. He was ridiculed for this thought as it would require a pollinator with a 12 inch proboscis, which was unheard of at the time, but years later a large moth (a form of sphinx moth, I think?) was observed visiting a Ang. sesquipedale; it had an extremely long proboscis, confirming Darwin's theory. This was the first time that a pollinator was theorized to exist based simply on the formation of a flower. Unfortunately, Darwin had died before this moth was found, but it has ultimately immortalized him due to this find!
Really nice flower! I forget - is there any smell? I have a small clone of this and hope it will do as well as yours!
Steve