The 24 has the simplest optics and works the poorest of all at f/5.
The 21mm and 17mm are very good, with only a very mild astigmatism in the outer field (I think the design was optimized for f/8+).
The 13mm is the weakest of the series, contrast-wise, and has some edge of field brightening, though it is better than the 24mm at the edge of the field.
The 10mm is a bit newer design and better-optimized for f/5 than the 8mm or 5mm.
The 8mm and 5mm both have smaller field stops and function OK at f/5--about like the 13mm, but a trace better at the edge.
In general, how they fare in the f/5 scope is the presence of a bit of lateral field astigmatism. This is very common in eyepieces from many companies--many of which are more expensive.
I think the Vixen LVWs (now discontinued) were the inspiration for many lines of 65-70° eyepieces on the market today. The Hyperions are the equal of most of them.
My comparisons were all made at f/5 with a coma corrector, so coma did not enter the picture.
With no coma corrector, the edges might display a bit more aberration because the coma will add to the astigmatism.
And they do have issues with short focal lengths due to field curvature. I think they may have a tiny bit of inherent field curvature that adds to the large amount of FC in short focal length scopes.
In a 10" f/5, though, FC won't be much of an issue. In most refractors or short reflectors (like the aforementioned 6" f/5), FC can be obtrusive.
My dob has a focal length of 1825mm, so FC wasn't noticeable.
These are quite comfortable eyepieces to use. You might find the Fine tuning Ring makes the exit pupil a bit harder to acquire, but this is not an issue in seated observing.
After all these years on the market, I still think they're OK as a step up from entry-level eyepieces, though I don't usually recommend the 24mm.
But how many other widefield eyepieces accept camera adapters directly, or use both 1.25" and 2" filters? And have long enough eye relief for glasses? Not too many
Edited by Starman1, 23 November 2018 - 06:47 PM.