I wonder if one of these would help you Mike. Good price and f5. And it's an Astrograph.
When I rang Bintel to ask about getting one I was told by them not to buy it coz it is very similiar to my ED80 but f5, so I wouldn't benefit too much from it.
On a side note: Damn nice of Bintel to do that. They talked me out of buying something rather than just flogging product
Oh, the link:
https://www.bintelshop.com.au/Product.aspx?ID=7379