Well, most nights, sunlight still bounces off the moon before it hits the earth and its inhabitants. This could imply that the sunlight is only dangerous to a vampire prior to interacting with another solid object. If one is willing to assume that the lens and its various filters qualify as a solid object, that could explain the lack of death.

Presumably the only reason they don't employ this loophole on Earth is because an astronaut just walking around would draw unwanted attention.

Alternatively, perhaps the vampire keeps its back towards the nearest star at all times.