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All else being equal (regarding resolution from center to edge, contrast, transmission, color purity, etc...), if I had the option to see a real field of 77 degrees within an apparent field of 68 degrees, vs. seeing a real field of 77 degrees spread over an apparent field of 82 degrees, I would choose the former, since my eye would be able to take in the same real field of view far more comfortably, with less wandering of the eye required to absorb the exact same chunk of sky.

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You would rather have -11.7% angular magnification distortion than +6.1%? OK, I guess maybe I can see that, but where do you draw the line? How about an RFoV of 400 degrees in an AFoV of, say, 50. Of course there's a teensy bit of negative angular magnification distortion there, only about -700%, but it fits a lot of sky in 50 degrees! How much is too much?

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That's where "Majesty Factor" comes in!

The answer to your question is subjective, of course. For general viewing, even the larger distortion is not going to be noticeable. But if you want to do imaging or sketching, then it can be a problem.
I would say it gets to be a problem when you can see the stars appear to follow curved paths across the eyepiece field, or when the image of an extended object is visibly distorted.

Or, when you're trying to take accurate measurements. Or star hopping.

I didn't realize the Hyperion had so much distortion until I used the formula that Lawrence provided. By that token, I would think it would not be a problem for visual observing.

For a budget widefield eyepiece with great views in a convenient image scale, the Hyperion is hard to beat. If you want the least distortion possible in the wide field, and can afford it, get the Nagler or Ethos. If you want the most distortion-free field possible, period, then get -- an Orthoscopic? A Brandon? A Plossl?

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"Since the process of science generates more mysteries than it solves, I predict that we'll never learn everything: and we'll continue to generate new ignorance at the speed of knowledge."



"S.O.E." (Sauron's Other Eye), with 16" Royce conical mirror: A permanent work in progress.
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