many thanks
Basically, EzyStyles, the short exposure is 2x1 min the long 2x10 mins to the ratio would be about 10 to 1, which seems to be enough to allow me to get all the detail from the brightest to the faintest without "clipping" that is burning any out.
There is an EXCELLENT article about this in the latest Aust. Sky & telescope I got just today. Its called Of Colour and Composition, by Tony hallas, starts on page 80. On page 81 he talks about clipping and the loss of detail it causes. I thoroughly recommend the article.
Scott