Hi Chris,
I have a couple of Hyperions which I use with my SGT - a 21mm and an 8mm. The 21 mm gives me x71 and with a 68deg. AFOV it is great for larger clusters etc. I did try the 5mm but at 300x, I could not get a sufficently good image in the suburban polluted skies to make it worth while. So I swapped it for an 8mm which takes me up to 180x which is quite good for planet viewing in suburbia.
When I go bush, that will be a different matter -
but I have to save for a few more bits and pieces before the 5mm gets a guernsey.
The lenses themselves are rather bulky and weigh in around 350-400g, however, they give excellent images.
I have pondered the use of rings to change focal lengths, but the thought of pulling the lens apart to insert a ring, or 2, or take them apart while out observing in the field sort of leaves me a bit reticent. If I was in an astro-shed, that would be a different matter. Nevertheless, it is an option well worth considering.
I guess you have looked up their other properties so I needn't repeat all that detail here.
In summary, I think they're good eps.
excellent value for the money.
Robert