[davidmanze]

While I don't test it, it feels likely that almost all ultra-wides suffer from coma at max. aperture.

Lenstip's coma test shows that the Samyang 14mm F2.8 does not suffer from coma even wide open on FF!

 

I bought the lens expressly for land/starscapes, but I forgot to check that parameter before ordering,   

 

     so a minor Yee haw moment!   

 

  Let's see if the Samyang 20mm F1.8 suffers from it, if it's of a low order it will be a very sort after lens for astro-photography, MF for infinity focus is no problem (forgiving Samyangs some somewhat lackadaisical calibration of this parameter, leading to DIY calibration  Utube videos).

 

The Nikon AFS 20mm F1.8 unfortunately does suffer from coma least ways on FF!