There are always those who enjoy to confuse apples with bananas.
The thread subject is: "ATC requests cloud tops at night "
and not: ATC requests TO CALCULATE cloud tops at night.
All that ATC wants in this case is:
Pilot Visual report, using Pilot cockpit windows vs Pilot altimeters, during climb or descent. During level flight just say you are bellow,above or on top.
PS
If you can not make the difference between night-sky
(with or without moon, the darker the more stars should be there ! )
opposite to no-sky-visible due to in-cloud conditions then no calculation will help you.
