observation - How to calculate the LST of an astronomical object at a given height above the horizon [in degrees]?

My situation:

I want to observe M52 at RA = 23h24m48s, DEC = +61deg35arcmin36arcsec from, let's say, Calar Alto at 37.23deg N and 2.546deg W.

How can I calculate the Local Sidereal Time (LST) at which M52 is at 40degrees height above the horizon?

Thank you for your help!