What is the answer? I've always gone with a short o, which kind of makes sense given that "Mon" is short for "Monday," though I'm actually using a different o than the one in "Monday."And is "Mon-El" of the Legion of Super-Heroes pronounced "Mon-El" or "Moan-El"? Pretty sure I got that wrong for decades!
Embarrassingly, I wrote a whole book set on 40 Eridani A II thinking it was pronounced "er-ih-dan-ee" (and "er-ih-dan-us"). At a planetarium, I asked an astronomer to show me the star, and he corrected my pronunciation. But I've studied Latin for years-- I should have known better!And a lot of people seem to think Eridani (possessive form of Eridanus) should be "air-ih-don-ee" or "air-ih-dan-ee" when it's actually "eh-rid-ah-nee."