feature request: plot fixed altitude line #24
Description
I have limited visibility due to hedges and buildings, it would be really useful for me to be able to add a line of ~40 degrees above the horizon to charts that I'm producing. Having read all the options available to me, I don't think this is possible: the closest I could find is to use grid_coords=alt_az and mentally block out everything below 40.
Ideally, beyond just a line at a fixed altitude, it would be good to either not plot anything below that line or to mask it off with a grayscale. Since objects below this altitude line aren't of interest to me, I was hoping to have a visual indicator that "you can't see these things".