I've had all my eyepieces for several years, now and used them frequently in a 12.5" f/5 (f/5.75 with Paracorr) and a 4" f/7 triplet apo.
All the eyepieces have been used often, with the 3.7mm Ethos seeing the least use, but still used many times in both scopes.
Sites have varied from 20.9-21.8mpsas skies.
I have some seat-of-the-pants comments, and the only reason I make this post is to see if other users have noted the same things and to note some misgivings.
There is no perfect eyepiece, and an eyepiece need not be perfect to be enjoyable to use. My use is 99.9% deep sky use, not planets and Moon.
All but one of these eyepieces exhibited slight chromatic smear of star images at the edge, but that aberration is so common in eyepieces I just ignore it unless it is egregious, which it isn't in any of these eyepieces.
I wouldn't hesitate to recommend any of them to another observer, though I might not recommend some of them for an f/3 scope user.
So, I will post what I like, and what I don't like about each eyepiece. If the eyepiece is glasses compatible, my comments include glasses use because without glasses I cannot honestly evaluate an eyepiece.
Ditto the use of a Paracorr in the dob. Without a Paracorr, I could not evaluate the edge of the field in the eyepieces because I would blame poor image quality on the eyepiece when it is really the scope's fault.
These will solely be my opinions and not applicable to other scopes, users, and sites.
Feel free to disagree or point out something I omitted. Do point out what scope you use, however.
30mm APM Ultra Flat Field:
What I like:
- Flat field
- sharp star images
- superb contrast
- ease of use
- lightness of weight for its focal length
- edge of field control of aberrations (No CA or Astigmatism!)
- cheap price
- no lower barrel undercut
What I don't like:
- blue stars have less luster than in, say, the 31mm Nagler
- only 70° field
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22mm Tele Vue Nagler Type 4
What I like:
- ease of use--very comfortable.
- sharp star images
- ultra-wide field
- Instadjust eyeguard when sharing the view with others--<1 second, one-hand adjustment.
- brightness of the star images
- immersion in the field
What I don't like:
- the low power it produces, which means it doesn't get used as much as other eyepieces
- weight. This is one dense eyepiece.
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17.5mm (17.2mm) Baader Morpheus
What I like:
- comfortable to use
- 98% of the field very sharp
- good contrast
- very light weight
- kerfs on lower barrel
What I don't like:
- narrower apparent field than all the other Morpheus eyepieces
- eye relief a bit too long and I have to use o-rings under the eyecup to make it the same as my other eyepieces
- stars in the last 2° of field astigmatic
- No-Man's Land for magnification--always too low or too high in my scopes.
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14mm (13.9mm) Baader Morpheus
What I like:
- superb contrast
- superb light transmission
- excellent sharpness until very close to the edge.
- ultrawide field
- light weight
- perfect eye relief for me with my glasses right out of the box
- kerfs on lower barrel
What I don't like:
- that it isn't a 13mm. 14mm is just a *trace* too low a magnification
- slight edge of field CA.
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12.5mm (12.4mm) Baader Morpheus
What I like:
- One of the sharpest [star images] eyepieces I've ever used. Globular clusters resolve to the very core.
- superb contrast. About as little scattered light in the eyepiece as I've seen.
- a great magnification for lots of objects.
- ultrawide field
- ease of use
- light weight
- kerfs on lower barrel
What I don't like:
- too close to my 11mm in magnification
- seems a bit darker than my 11mm and 14mm
- 12.0mm would have fit my magnification scheme a little better.
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11mm Tele Vue Apollo11
What I like:
- 85° field
- image contrast!
- very sharp star images
- light transmission
- eye relief
- zero vignetting
- the thinnest blue edge to the field that I've ever seen in an eyepiece
What I don't like:
- the 2" steel adapter. It could/should have been aluminum to save weight.
- slight astigmatism at the very edge
- field stop not in focus for my eye.
- very slight field curvature in my scope.
- it's not a 10mm
- undercuts on 1.25" barrel and 2" adapter
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9mm (8.9mm) Baader Morpheus
What I like:
- Ultrawide field
- exit pupil position narrows visible top of the eyepiece to a thin black ring around the field for a floating in air effect
- light weight
- very good contrast
- sharp star images
- works great on a lot of DSOs
- very bright image for its focal length
- kerfs on lower barrel
What I don't like:
- eye relief was too long until I tamed it with an o-ring under the eyecup.
- edge of field CA
- *slightly* softer star images than the Morpheus focal lengths on either side.
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7mm APM XWA
What I like:
- 100° field
- very sharp star images to *just* shy of the field stop
- Superb contrast
- excellent control of light scatter
- entire field is easy to use
- smooth lower barrel and smooth 2" adapter--no undercuts
- light weight for focal length and field of view--can use as a 1.25" with no risk to the barrel.
What I don't like:
- needs another mm of eye relief.
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6.5mm (6.7mm) Baader Morpheus
What I like:
- superb contrast
- superb light transmission
- excellent sharpness until very close to the edge.
- ultrawide field (79°--the widest of the Morpheus)
- light weight
- perfect eye relief for me with my glasses right out of the box
- kerfs on lower barrel
What I don't like:
- magnification doesn't match my scopes well.
- edge of field CA
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6.0mm Tele Vue Ethos
What I like:
- ultra sharp right to the field stop
- superb contrast
- easy to use without glasses
- no noticeable astigmatism at all
- extremely slight CA right near the edge
- light weight
- field seems wider than 100°
- used as 1.25", there is no undercut on the barrel
What I don't like:
- the 2" skirt has an undercut
- the 2" skirt is not removable
- it can't be used as a 2" eyepiece in the Paracorr without adding a long barrel extender
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4.5mm (4.8mm) Baader Morpheus
What I like:
- the sharpest of all the Morpheus
- flat field
- superb color rendition for planetary nebulae
- very good contrast
- light weight
- kerfs on lower barrel
- perfect eye relief for me with my glasses right out of the box
- ultrawide field
What I don't like
- slight CA at the edge of the field
- slight barrel distortion (noted in daylight--at night the field is too narrow to really notice)
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3.7mm Tele Vue Ethos SX
What I like:
- very sharp star images
- excellent contrast results in very faint details seen in planetary nebulae
- hyper-wide 110° field results in longer views between nudges of the scope
- light weight even though a long eyepiece
- CA seen only at/near the very edge
What I don't like:
- undercuts on 1.25" barrel and 2" adapter
- 110° field was unnecessary and 100° would have been enough, and less head movement would have been required.
- the shortest eye relief of the Ethos series. It's OK, but less than the 6-21mm Ethos.
- the fact I can't use 500x every night I go out.