Frankfurt FRA to HHN Airport?

If your flight is at 08:00, you might want to go to Hahn the night before. Buses leave the main train station in Frankfurt on a regular basis. Check the Bohr website for schedules. There are budget hotels and hostels at Hahn.

The bus takes about 1.5 hours.

Since you are likely using RyanAir if flying from Hahn, you need to be really really careful to meet all their deadlines and restrictions or expect to pay handsomely not to. In the worst circumstance, such as arriving one minute late your ticket will be void and you will have to buy a brand new full price one for the next flight going your way that has a seat free.

But you won't be late. Or have carryon that isn't. Or have to check luggage at the airport without buying in advance. Or not having your boarding pass printed out before arriving.

Here is the schedule of buses leaving Frankfurt or Frankfurt airport for Hahn. Note the schedule is different each day. Montag is Monday, etc. Abfahrt means departure; Ankunft is arrival. As you can see, there are numerous bus connections arriving in Hahn before 8 AM, but they leave Frankfurt really early.

We flew out of Hahn in June on a 7 am flight. There is a hotel on site, across the street from terminal. Reasonably priced and a decent room. We prepaid so no need for checkout. Just leave the room and walk across the street. You might consider having dinner before you get to Hahn. Food options ar very limited!