Possible Clues:

• Eclipse descriptor
• Of moons
• With 45-Down, about 29 1/2 days
• Moony held by Fiennes retreating
• With 38-Down, recurring phenomenon lasting a few hours
• Sort of month
• Moon's blue and rare, but not extremely so?
• Appertaining to the moon
• Laurence is all moony about a French one
• Like some space missions