IMO the SW flattener is the best option for the ED80. There are specific models for each ED so make sure you get the correct one. Mounting is by threading on to the stock SW drawtube on either the single or dual speed focuser. There's also a wide adapter available for Canon to allow full frame coverage, not sure whether there is a Nikon equivalent. Adapters are now made to allow fitting of the SW reducer to alternate focusers, this one also allows fitting of filters.
http://www.firstlightoptics.com/adap...-reducers.html
Some info and photos of setui in this post
http://www.iceinspace.com.au/forum/s...67&postcount=8