[JBorrow]

That 'excellent seeing' is for sites that are chosen for telescopes. Typical seeing from sea level is much worse:

- https://www.ing.iac.es/astronomy/development/hap/dimm.html

- https://www.researchgate.net/figure/Fig-C1-Seeing-distributi...

- https://www.mdpi.com/2072-4292/15/9/2225

Around 1-2 arcseconds is 'good' seeing in your backyard. There is a good reason for telescopes to be on some of the tallest mountains on Earth.