Hi all again,
Ta for the input.
As Kevin mentioned, I already have an 8" f/4 Newt.. The coma it produces in my 30mm 68deg. EP is not a problem for me.
For me, I think these aberrations are overstated and overrated. When the object is close to the edge of the FOV you will move the scope to accommodate it, regardless of the quality of the image at the edge with visual use! I don't mind the coma and even some astigmatism in the eyepiece for this reason. A coma corrector is wasted on me as they also kill photons.
Remember, I am wanting to get the WIDEST rich field I can (to within reason and exit pupil). From the replyies, field curvature at low powers is the biggest aberration with fast refractors. From my reading and dissection of binoculars, this is delt with by introducing a smaller field stop to the eyepiece of low power binos. The AFOV tends to be bigger in higher power binos than low power ones of the same aperture to remove the field curvature aspect. Most binos use the Erfle EP design, which is capable of delivering upto 70deg, even 80deg AFOV, but this would be lost in binoculars. Efles produce a fantastic wide field image in slower instruments than fast.
Take my 11X70 binos. The FOV is 4.5deg, giving an effective AFOV to the EPs of 49.5deg. That's smaller than a standard Plossl EP of 52deg.
Now, as I understand and am happy to deal with the aberrations of optical systems, like my 8" f/4 Newt., so a fast refractor,
for visual purposes, I'm seeing as quite a feasable beastie.
I completely understand the consequences of such aberrations to astrophotography. My visual philosophy sees me happy with them though,
.
Kevin's new 80mm f/5.5 semi APO looks very interesting...
