Hi Barry,
Thanks very much, I appreciate it.
The UV/IR coverage on this glass allows some UV light from 320nm to 350nm and then from 380nm to 400nm to reach the sensor. I suspect that this can lead to star bloating in long exposures if it is not blocked by another filter.
Many of the light pollution and band-pass filters available are advertised with transmission graphs showing zero or near-zero transmission across the UV.
When these filters are tested by independent third-parties, the resulting transmission graphs often tell a very different story by showing that at least some UV light passes through, in varying quantities. I recently switched to an Astronomik CLS and found that it is definitely one filter that performs as advertised.