The TC - 200mm combination is not going to give you a very large image. In fact, it requires 2500mm focal lengeth to deliver an image 25mm in diameter, of the Moon, which is only about 30 arc-minutes in diameter. Therefore, even a 2.0 TC, which will change your f2.8 lens into an f5.6 at 400mm, will give you in image about 4 mm in diameter. That's pretty small for the money. Sorry.