I have to work with a logo that is unbalanced all the time.
The way I deal with this is by centering based off of the heaviest element in the image. In your case this is the circle.
This works because, at a glance, it often appears as though the object is perfectly centered.
In this example, the green line shows my "center" while the red line is closer to the object's true center.
As you can see, I ignored the blue lines to center the object. This decision was based off of my personal opinion and a bit of user testing.
In the case of your graphic, I would take the same approach.
Even though the red line shows the center of your graphic, it looks very off-balance since all the weight is in the circle.
Try center based off of the green line (center of the circle).
In the end, you have to like what you see. So if you think it looks better one way over another, go with your gut!