Hello Yunti, When you are mooning over someone (or in this case his photograph) it means you are spending/ wasting time on someone you are in love with or have feelings for instead of doing something else. 'Lover's procrastination' so to say. I hope this helps. Aleks

Thank you so much.

Hello, "Mooning over" in this case means admiring the object (in this case the photograph) in a loving manner. Hope this helps!