gui_root.py having problems in some machines

[briancatraguna]

Some machines will have this error log

File "/usr/lib/python3.8/tkinter/__init__.py", line 2270, in __init__
self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use)
_tkinter.tclError: no display name and no $DISPLAY environment variable

While fixing the problem, proceed to use star_simulator.py, you can change the FOV settings, focal length and the pixel size in the code