How to shoot stars with a gfx100s fashion camera?


I think my problem is original: I am a photographer, but I usually shoot fashion, portrait , etc
So I have a camera that I think is quite good: Fuji GFX100S with 5 lenses. ( it’s medium format, 11,000 pixels by 8000, 43mmx33mm sensor, 100MP, 3.76 microns each pixel , I can set exposure up to a few minutes , never tried longer, in body stabilization and lens optical stabilization , it’s quite a good camera …)

I have a Manfrotto standard tripod with the usual screw for most such cameras.

I took it out tonight and I got Jupiter’s satellites and the andromeda galaxy quite easily. (I used the 80mm f/1.7 portrait lens and the 250mm f/4 beauty lens) (I also have a 23mm f/4 , a 50mm f/3.5 and a 45-110mm f/4)

I would love to shoot some beautiful nebula and clouds.

I am limited in exposure time by the earth rotation.

Given I have all of this already I wonder if I should just get a system that compensates for the earth rotation. (And to save money too VS getting a telescope, camera etc).

Questions :
1. Any advice on what to get that I can mount in between the camera and the tripod? (It would be to just take pictures for fun, ideally a budget of a few hundred dollars)

2. Also I thought maybe I should get a telescope and mount the camera on the telescope instead of using my own lenses. Would that make the pictures better then with my existing fashion lenses ? Why? If so what to get that mounts easily? Adapters ?

3. Once I adjust for the earth movement what will limit the quality of the pictures ?

Thank you for the help and sorry as I have nobody local in person to ask.