Houghy,
For a multiple Optic System thats outstanding. You would be happy with that in an Apochromatic Refractor.
In addition Nat wouldn't have quoted the figures if it wasn't.
I am not 100% sure what the difference is between the 500 and 503 model but I don;t think its much. Same horse different jockey I guess. I think the 500 model was what was released to the European Market and the 503 was the model released to USA. Regardless the 500 model sells new in the UK for about £650 to £700 and you have no guarantee to get 1 this good optically. What part of "BUY THE SCOPE" are you not getting
hehehe
If you don't hurry I am gonna buy it and I am serious
CS-John B