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The Hyerions seem to work just fine down to about f/4.5 in a newtonian IF the newtonian is used with a coma corrector. I think a lot of what the Hyperions get blamed for is the presence of coma in the outer fields.
True, like many less expensive eyepieces, they are not completely free from edge of field astigmatism, and there may be better alternatives if one is looking for better edge correction.
But, for planetary use, where the planet is likely to be confined to, say, the center 50% of the field, and the requirement is for long eye relief, they'd do fine.
Now, the Chinese eyepieces sold as Astrotech AF70/Celestron Ultima LX/Olivon 70/Arturus Ebony and many other labels are, in my opinion, a bit sharper in that center 50%.
And if the purpose is a long eye relief eyepiece for planetary use, an economical solution might be the Meade HD60, the Celestron X-Cel LX, or the BST Dual ED (sold as Astrotech Paradigm, Agena Starguide ED and many other labels).
And if price isn't a factor, the TeleVue Delite may be just the ticket.
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