how can I calculate the end of shabbos for specific locations?
The rule is when you can see 3 medium stars shabbos is over. Sorry I can’t offer a universal formula. Is there a specific location you are wondering about?
Same as NY, NJ.
Perhaps he’s referring to the differences in tset hakokhavim in different latitudes. I recall from yeshiva that R’ Moshe Feinstein had a rule (I’m guessing for the Lower 48) that it was never more than 50 minutes after sh’kia.
Understood. The Rabbi never approved following a specific formula such as x degrees… There are different factors that affect darkness and we can’t give a generic Psak for the entire country.