Mag., Alt., Seeing?

[Kirkus]

I've noticed on many astro images that are shared on the internet, certain specs are included. The f-ratio, focal length, etc. I understand how to figure out. But how do you figure out the magnitude, altitude, and seeing conditions? Are there mathematical equations to be learned or are these just best guesses?

[iceman]

The magnitude and altitude are from planetarium/starchart programs.

Seeing is an educated guess.

[Kirkus]

Oh. Of course! That makes sense. Thanks.