I only grow two Asters. Frikartii which flowers earlier in the season and this one, Little Carlow, which flowers so incredibly profusely that it is possibly the best thing there is in late September.
It's all about the light. September sun, though bright, doesn't wash out colour the same way it did back a month or two.
Doesn't mind it dry (and we have been dry) this should go on for a few weeks yet.