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The GSO SuperViews are a great eyepiece for their price! I've got the 30mm & 15mm- These are the EPs I use the most.
I've used them in an 8" f/6 dob too. They perform better in a scope of this focal ratio or slower as a fast scope will begin to reveal the astigmatism they are prone to. In my f/5 & f/4.5 scopes, the image starts to degrade towards the edge of the field of view. Yet I'm very happy with their performance until I get a better quality EP. The distortion is very tolerable.
Mind you, as a comparison, I've also tried an Orion Q70 30mm in my 17.5" f/4.5. It is three times the price of the GSO. The image quality was appauling!
I've also had a Nagler 30mm EP with its 80deg FOV in the same scope- also appauling- way too wide and impossible to overcome the astigmatism the EP/stumpie light cone combination creates. I also needed to move my head to see the whole image this EP provides, not just my eyeball- our eyes can see well within a 68degree range, NO coincidence!
There is a balance that needs to be achieved with a scope's f/ratio and the FOV of a given EP. These giant FOV eyepieces are really best suited to long focal ratio scopes, like an f/10 SCT, where the cone of light it produces is very tight. But the need to move your head to see it all still applies, regardless of the focal length of the EP.
Suzy, I've had a go of an Andrews 30mm 80* EP in my 17.5" f/4.5. It performed surprisingly well. Actually much better than the Nagler!
Another thing about these high end long focal length EPs is that they can get really, REALLY big and heavy- try to balance a 1.5kg lump of glass on the end of your dob!
MBO, if you are after a good short focal length EP, have a look at the Williams Planetaries, or the TMB planetaries, the former have a 55* FOV, and the TMB's 60*. The are relatively inexpensive, but perform really well, with a very comfortable eye relief, meaning you don't need to rest your cornea on the eye lens of the EP to see into it. I have a TMB Planetary 6mm- I love it!
What I'm getting at, you don't need to spend big bucks to get good EPs. Understand how our eyes work and their limitations, the physical mechanics of scope optics, a little research and a little tolerance of aberrations, and you can get a really good set-up without spending big bucks.
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