Calculate right ascension in Zenith at this moment in my location I've been searching on Internet about how to calculate which RA is in zenith at a given location in a given time but I haven't find anything (or maybe I don't know how to search).

Using my star finder I have not draw any conclusion.

How can I calculate which RA is on zenith on a given location in a given time?
Right ascension at Zenith should always be your local sidereal time.