How should I draw the horizon on a sky map?

Is there any way of drawing the horizon on sky maps similar to the one attached?

This is the complete chart in Stellarium:

• If zenith angle is 0 degrees in the center and 90 degrees at the edge and you've been careful to plot your star map in polar coordinates with $r$ as zenith angle and $\theta$ as azimuth (or negative azimuth) then draw the zenith angle=90 degrees circle as your horizon. However, if all of that is not true, then your question should really be "How to convert a star map in RA/Dec to a sky map in zenith angle and azimuth?"
– uhoh
Jul 18, 2021 at 16:01
• I added an image of the sky map with the horizon (the green circle). The map is a oblique stereographic projection (I think that's what it's called). I don't know how to make my question more specific, I want to know if there is any way of drawing the horizon without knowing the latitude of the observer.
– John
Jul 18, 2021 at 16:33
• I see, thanks! I think you will need to find a different projection. I haven't used Stellarium in a long time, but I'll bet there is an option to make a star chart for you. I think that viewed like this it's impossible to draw a horizon and make a reasonably useful star chart.
– uhoh
Jul 18, 2021 at 16:38