everything is brought to the top point by jerryy
Perhaps the hint that "seeing" the clarity of the sky without thermals (for example in the second half of the night in summer when the country has cooled down) brings the chance for good photos.
This works best far away from large cities with large amounts of light pollution.
After many AF attempts, I gave up and only use manual optics whose infinity is very well adjusted. But you then have to enter “Photo without lens” on the camera and set the manual focus.
An example would be a 23mm or 35mm TTartisan which is available for a low price; and they have three screws on the circumference of the distance ring with which you can actually adjust the worm to infinity with the scale at the stop.
The 300 rule actually just says "the longer the focal length, the shorter the possible exposure" Example 300/ 35mm (or 500/ 53mm full format) = 9.6 seconds so a maximum of 10 seconds. Since the "rule" is 300/12mm = 25 sec (500/18mm full format) =28 sec, ?
So you can expose with 8 mm then 38 sec on crop 1.5 and even 41 sec with 12mm full format!! BUT THAT IS WRONG!
The limit of 20 seconds (for short focal lengths) or better 15 seconds should NEVER be exceeded. Anyone who adheres to this also receives round stars !