For those of you who may have an SM40/Tmax and want to mount it on your ED80, here is a drawing of an adapter that you can take to the local machine shop and get them to make. I priced the genuine adapter at $400, and more than one vendor suggested to simply get one made rather than buy it
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I got mine machined for $50 cash, but you may be able to negotiate it for a case of beer
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Remember you'll need an appropriate blocking filter as well (either a Coronado BF10 or Lunt B1200 for an ED80).
Check the outside diameter of the dew shield on your scope... mine measured 116.0 to 116.2 so I made the adapter 116.4 which is a nice fit given the dew shield is plastic and the adapter is aluminium so there will be some differential expansion with temperature.
I plan to secure mine to the scope with insulation tape around the outside, but if you want to and can source some small plastic thumbscrews, you could drill and tap the outer lip and fit them as clamp screws.
Al.