Certain Pokémon are always going to be difficult to catch for one reason or another in Pokémon Go, with Ultra Beasts like Celesteela near the top of that list since you need to find a Raid or get an invite to one to encounter this ‘mon in the first place.
As such, Celesteela is a real pain to catch since it is exclusive to five-star raids in the Southern Hemisphere which means it is harder to access since fewer people live there compared to the Northern Hemisphere. Your best bet to catch the Steel/Flying Ultra Beast is to try and secure a Remote Raid invite from another player in those areas—something that is easier said than done.
Pokémon Go Celesteela Raids: How to get a Remote Raid invite
If you want to get an invite to a Celesteela Raid in Pokémon Go, you should browse social media sources like Reddit for active players offering to add people and invite them, join a Remote Raid-centric community on platforms like Discord, or try and use trusted third-party apps like Poké Genie.
According to multiple sources, including the World of Statistics, only somewhere between 10 to 13 percent of the world’s population lives in the Southern Hemisphere which encompasses most of South America, the lower portion of Africa, and a good chunk of Oceania including all of Australia and New Zealand. This severely limits the number of Celesteela Raids available for you to potentially get Remote Raid invites to since the demand outweighs the supply—especially with Shiny Celesteela on the menu.
Using a third-party Raid app such as PokeRaid or Poké Genie is usually your best bet to find Remote Raids for rare Pokémon. In this instance, however, the demand is so high that some players are reporting queues for Celesteela Raids that reach over 20,000 players easily—with some posts citing only one or two Celesteela invites popping up per hour on the apps’ servers.
Using r/PokemonGoRaids will give you a decent shot as players are actively sharing Celesteela Raid invites frequently, and you can grind some other active Raids while you wait for new posts. You might have luck looking on websites like the Friend Finder or the community Friend Code document for people to add in those regions, though that is almost like cold calling a near stranger and asking them for directions.