I used this to calculate the scale info:
http://www.skyatnightmagazine.com/field-view-calculator Gives me a FOV of 19.01' x 14.2' which could be my problem. I've realised now, thanks to you, that I stupidly had my numbers swapped. I was using the scale values for my ED80 on my RC8.
Move along now, nothing to see here....
