Thanks Malc - that was my thought too and tonight I think I tracked down the culprit. While the star is considerably dimmer than EC and at its brightness there would be little at the red end with a DSLR, I think I'll have to bin these dammit. Really annoying with the star at a very interesting phase and clear skies as rare as hens' teeth.
Ah well, if it's fine tomorrow night I'll try a radically different orientation just for peace of mind. Thanks again!
Cheers -