"Sphere" shadow and light practice

One of the most basic exercises in drawing is the sphere in light. The perfectly captured sphere shows an understanding of shadows, reflected light, curvature, and dimension in a single subject. In theory, once mastered, the same principles can be applied to replicating any three dimensional object.

As a digital artist with few skills in the traditional arts, I thought this exercise would be a good place to start learning how to use the tools. In my case, I wanted to gain a mastery of the skill of illustration, not a set of fancy pens / charcoal / marker.

For this sphere, I'm imagining the light coming from the upper right. The shadow should be narrow, since the light is coming from the top, but not as narrow as I have done it. The distortion in the shadow makes it seem like the ball isn't a perfect sphere. Also, I probably could've gone with some darker values with the shadow, since I'm using an ordinary Bic pen.

I want to use crosshatching to provide the shading. Cross hatching requires really good parallel lines, a skill that is clearly NOT demonstrated here, especially as the lightest shade value fades into the direct light. 

Drawing circles is REALLY hard, apparently. The way I kept missing the circle gives this ball a cartoonish effect of movement, as the lines seem to indicate some kind of vibration.