You will see them at every tournament – they struggle and debate to get on the line directly square to the target. But does it really matter whether you are square to it or just a yard or two off?
There are several possible reasons to be in this special position. It is the point that is closest to the target; any movement to the side will result in you shooting a longer distance. Also if you are off to the side then the circular target will appear to be an ellipse from your viewpoint, thus making the target physically smaller to aim at. Let us look at each of these in turn to see how much difference they actually make.
Let us start with the fact that you will be shooting a longer distance. This is because as everyone knows from their school days with Pythagoras the hypotenuse of a triangle (the side opposite the right angle) is the longest of its sides. To work out this extra distance let us suppose that the shooting distance is x metres and the new distance is y. If the displacement from the centre line is d then we can use Pythagoras’ Theorem to work out the new shooting distance. The table below details the extra distance shot for a sideways movement of 1, 2 and 3 metres (which is an awful lot) for three distances, a short, long and intermediate distance.
I shoot a 34 lb. bow and the difference in my sight mark between 40 m and 50 m is 25 mm. So if I was 2 metres off line at 50 metres, shooting an extra 40 millimetres I would have to change my sight mark by approximately one tenth of a millimetre. I think that even the best archers would be hard put to it to see the difference that made; in fact those people probably shoot faster bows giving flatter arrow flight and, therefore, even smaller changes in sight marks.
The other problem one could encounter is the fact that as you move to the side the circular target is going to look like an ellipse and therefore smaller than when square to it.
This apparent change is governed by the Cosine Law. The change being the cosine of the displacement angle marked a on the diagram. Calculating the apparent change in horizontal width (the apparent height stays the same, of course) the results appear in Table 2.
I find it difficult to believe that many people could notice even the greatest of these, a 4.1 mm change in width of a full size boss, and this while standing three metres from the centre line at eighteen metres. In practice it would look odd to stand more than about a metre off at this distance.
So why do archers struggle to get that central position? I can only suppose that they have a mental image that this must be the best position, which it is, but by so little that it really makes no physical difference to anyone’s shooting.