Illumination at Dusk minus 30

[Blackcloud6]

Dusk begins to reduce spotting range starting at 45 minute before.  So, at dusk -30 the range is 4 but night is not in effect.  Can one fire illumination in a non-night turn?   I ask because the example on page 41 says "At night..."  But the rules are otherwise silent.

I'm of the opinion that Illumination should only be allowed on night turn as the light would not be as effective if there still is some daylight.