"in" or "on" a clear night?

English as a Second Language English Vocabulary, Grammar and Idioms
1

Dear all:
My name is Thomas. I have a question about the usage of “in” and “on”, when referring to the morning/afternoon/evening/night

I saw one sentence in the book in which it says “On a clear night, we can look up at the sky and see into space.” I thought the preposition should be “in,” since we usually say “in the morning,” “in the night.”

So in this case, is it simply because there is an adjective “clear” to make the night more specific, thus using “on” would be more appropriate? Will it bother to still use “in” as in this case? What may be the difference?

Thank you very much!

2

As you say, the preposition is modified by the adjective.

in the night
in the middle of the night
but
on a dark night
on a stormy night
on a star-studded night
on that fateful night

The exception is where you add something else, like ‘sky’ (so you are talking about the sky rather than the night)

In the clear night sky
in the star-studded night sky