Baader Hyperion Aspheric

[cajen2]

Does anyone have any experience of these? I'm interested in a mid-price, relatively wide- angle EP in about the 30mm f/l range. I'll be using it in a StellaLyra 8" dob (f/6).

[Louis D]

Since the 30mm APM UFF is so much better in the same price range, I don't know why anyone would look at the 31mm Hyperion.

[cajen2]

Yes, I've just been looking at that. The WO SWAN 33mm is a good price and seems to get good reviews too.

[Louis D]

At f/6, the WO SWAN is going to start showing astigmatism at around 60% out and be a complete blur in the last 15%.

The APM UFF is going to be perfect edge to edge.

I guess it depends on your tolerance for edge imperfections.  If you nudge your Dob often enough, you could keep the object in the inner 50% of the WO where it will be sharp.  The problem I found with these types of eyepieces is that they fail as finder eyepieces because stars look like nebula in the outer regions, so it makes it difficult to locate globular clusters and planetary nebula and center them for higher power viewing.

Compare the lens design of the WO SWAN (5 elements in 4 groups) with the APM UFF (9 elements in 5 groups):

The APM UFF is a technological tour de force.  It employs a novel telecompressor stage before the field stop such that the field lens (40mm) is larger than the physical field stop (30.4mm), while the effective field stop is larger (36.4mm) than the physical field stop.  This keeps the eyepiece very narrow for it's focal length and AFOV while allowing for near perfect correction.

The 30mm APM UFF is so good, I swapped out my venerable 27mm Panoptic for it in my A-Team eyepiece case.

Compare that to the 35mm Baader Scopos Extreme which is a giant beast with a typical telenegative stage ahead of the physical field stop, which is larger than both the field lens and the effective field stop diameter:

Edited July 9, 2022 by Louis D

[Don Pensack]

+1.  What Louis said.