Non-linear line for 90 degree line

[MichaelCowieSeequent]

I have been using your polar grid stereonet feature and it works perfectly, however I have a black grid overlay on top of the stereonet which draws four lines from the center of the stereonet at 0, 90, 180 and 270 degrees. Because of this, the appearance of the non-linear lines become clear. Right now I would like to report that one of the polar grid lines do not display properly.

Let's take your polar overlay example for demonstration, located at your github repository

When executing the program, I have drawn two lines that represent the x and y axis going through the center point. Here is a drawing of it,

From the image we can see the straight line is slight above the dotted line.
From what I can see so far, all other lines are fine.

I will begin to solve this problem now and if I solve it, a pull request will be made.

[MichaelCowieSeequent]

I have found the problem.

In the method set_longitude_grid located in stereonet_axes.py, you have a line which does

locs[-1] -= 0.01 # Workaround for "back" gridlines showing.

Once this line is deleted, everything works fine.