Hello and thank you for your words and for the warm welcome!
The exposure time for this kind of images is usually anywhere from around 10 to 30 seconds depending on light conditions and the lens you use - in short, for the longer focal length the exposure should be shorter for pinpoint stars, with the wider lens you can expose longer without the stars creating trails.
All the best!
RE: ⭑ Made of star dust ⭑ Hello Steemit Universe! ⭑