An oval is really a circle drawn in perspective. But don't be afraid of the word 'perspective'! Drawing eclipses or ovals can seem tricky. If it’s drawn badly, meaning that it’s not in perspective, it can really throw the whole work off. If it’s done well, the work reads as ‘true’. It's easier than you think to draw ovals correctly.

Because an oval is a circle in perspective, let’s first see how to easily draw a circle. 

If you were to draw a box around the opening and were looking straight down into the opening, it would be a square box. As you view point changes, the square box would shift with the lines of the box heading toward a vanishing point. In other words, a box in perspective. (To see the full effect of drawing a circle in a box, here is an article I wrote on drawing a circle)  https://www.quora.com/What-is-the-best-way-to-learn-to-draw-straight-lines-and-perfect-circles/answer/Elizabeth-Tucker-9)

It’s very hard to draw an accurate curved line. But its very easy to draw straight lines, hence, the box as a guide. We know that the round/oval shape will fit within the straight lines of the box or rectangle. Remember from math that between every two points there is another? Well, we can start to ‘carve’ the square/rectangle into smaller and smaller straight lines until our eye reads it as a curved line. When you do this, and you really take the time to look, you will see that those lines actually seem to be straight lines that meet up with its neighbor, which is also a straight line and so on….Some of those straights are longer or shorter than the one it’s ‘attached’ to, but it’s these attachments that make the illusion seem real. 

Now that you can draw a circle, let’s study some ovals. Take a glass or jar and place it on a table. If you look straight down into the glass, both the top and bottom are a circle, though one will be smaller than the other. If you aren’t looking straight down into the glass, because of perspective, the circles will appear as ovals. 

Again, take a clear glass and look at both the top and bottom of the glass. While raising and lowering the glass, you will see that the ovals in the clear glass will shift. One of the ovals (either the top or the bottom) looks rounder than the other. As you raise and lower the glass, your relationship to the glass changes. Because of the perspective change, you will notice that one of the ovals will be more or less round than the other. As you raise of lower your view line you will see these proportions change. For example, if your eyes are above the glass the back of the glass will be higher than the front, but as you raise the height of the glass the back of the glass will appear closer to the same line as the front of the glass . When you see the glass at eye level the top of the glass the top will be flat - you aren’t seeing into the opening and the view line is at your eye level. Notice what is happening to the bottom of the glass. If you move below eye level, the same thing will happen, only in reverse. The bottom of the glass will appear flatter while the top will appear rounder. Also, the front of the glass will be higher than the back of the glass.Take your time to really study this. If the glass is clear you will see the full oval. If the glass or round object is opaque, you won’t see the full effect of the oval going all the way around the object, but know that it’s there.

After studying the above, take a thin wire - the paper cut off a twist tie can work well for this - and place it horizontally across the center of the jar. Repeat the above by raising and lowering the glass and notice how the horizontal center line, though it hasn’t moved, seems to shift forward and back as you raise and lower your eye level. Crazy, right?! This is the power of perspective.

Place another wire vertically, at 90 degrees to the first, also in the middle. These two wires are on the diameter of the opening. The vertical wire is where you will drop the center line of the object, in this case a glass. If the eclipse was a wheel, such as on a car, then the verticals and horizontals would still be at 90 degrees to you but would head to the vanishing point. 

To create an oval we can take the idea of the box in perspective to create a visually convincing oval because the bottom line is that an oval is nothing more than a circle in perspective. To understand this better and see how easy it is to set up the perspective, click and watch the video below. It’s long but very thorough and easy to understand.  

https://www.youtube.com/watch?v=NMELt0J2Cno