No, there are no adapters to correct for this. The only correctors are for the scopes themselves. Recall that I mentioned that the focal plane produced by scopes is curved? The shape is somewhat like a bowl. But, the CCDs in our cameras are flat. Without some type of gizmo that can alter the shape of the incoming light from the scope onto the chip, if the centre of the image is sharply focused, the outer edge will not be. These gizmos are called field flattners for refractors and SCTs, and coma correctors for Newtonians. And they are not interchangeable either. Plus, with field flattners you need to get the right one exactly for your scope - diameter, focal length and focal ratio. AND these are only made for apochromatic refractors, not achromatic ones.
Wavy' mentioned that plossl eyepieces are ideal for eyepiece projection for Newtonians. GSO has a line of plossl eyepieces exactly for this purpose, complete with a threaded jacket to accept adapters
. Look at the Andrews Communications or Bintel websites for these. I have one of these 32mm plossls with the threaded jacket.
Alex.