I'm no mathemtician, but although more than one entry is allowed, you will probably have a certain style, and if you enter more than one then the votes that you get overall from voters may be split over several shots that you submit. You may, therefore, stand less chance of winning against others. I think the best approach is to wait until near the end of the period, then select your best shot. I entered mine early because I don't think I could take a better shot.
Someone is now going to tell me I'm quite wrong.
thanks for the advice Rob. But heck, who is doing this to win? I enjoy the process of coming up with entries