Provided the ceiling has not been painted before you can take a spray bottle to soak the surface, then use a scraper or drywall knife to scrape it off. *hint* Hold a small pail under the scraper as you go..saves a lot of cleanup afterwards.
Depending on the result, you may have to do a little skimming and nail pop repairs. I have had ceilings which were perfect after scraping and some that required a lot of skimming. Never know until its done