Adding to Tony Sizers comments on Thurday that OAS images should be entered, I have just had another look at competition rules -
http://www.nmm.ac.uk/visit/exhibitions/astronomy-photographer-of-the-year/rules/ (http://www.nmm.ac.uk/visit/exhibitions/astronomy-photographer-of-the-year/rules/)
There doesn't appear to be any reference to size limitations any more....................
So get submitting, you have until 19th July ;)
Hurry, hurry