Louis D

You might want to pick up a 45 or 90 degree correct image diagonal for terrestrial viewing to avoid image reversal. They're really cheap on the secondary market because they are packaged with so many department store scopes, so they're resale prices are very suppressed. I've got a few collecting dust that were tossed in with scopes I've bought over the years.

Spherical mirrors at f/8 and slower tend to be very close in figure to a true parabola, so the images can still be quite good if the price is right.

ChatGPT seems skewed toward commercial offerings. It never once mentioned Hubble Optics, Obsession, or any of the European custom Dob makers.

I really like its long eye relief, easy to hold FOV, and seemingly complete lack of SAEP. I will keep an eye out for EOFB in the APM. It is really bad in my 12mm NT4. One night, it was decreasingly hazy edge to center. I swapped it with the 12mm ES-92 and the haziness disappeared. I'm not much of a faint fuzzy hunter under dark skies, so I'm pretty insensitive to EOFB. I'm much more sensitive to SAEP because my pupils rarely dilate very far due to the increasingly severe light pollution around my backyard where I observe from. I'm hoping once the wife and I retire that we can move to a darker site not too close to any major cities.

I've yet to notice the EOFB in the APM. Of course, I'm generally not under dark skies like Mt. Pinos where I might be able to detect it.

I recomposited my 12mm to 14m UWA eyepiece ruler images together so it's easier to see the differences in presentation. It's also obvious which have objectionable SAEP. All are sharp to the edge at f/6.

I have the Morpheus 14mn rather than the 12.5mm. I haven't done that much head to head competition between them. They have very different distortion characteristics, so are a bit hard to compare. The Morpheus stretches objects close to the edge like 98% of well corrected astro eyepieces while the APM squashes them. As a result, the APM actually has the wider true field of view of the two. It's even a little wider than my ES-92 12mm due to it also stretching objects.

It's unlikely to have much impact on a 14mm 80 degree eyepiece since the 13mm Ethos is a 1.25" eyepiece (with 2" skirt), the 14mm Morpheus (measured 78 degrees) is a 1.25" eyepiece, and the 16mm Nagler T5 is a 1.25" eyepiece. I think they put it in a 2" housing to ease the design slightly. It really depends on the diameter of its field lens. Even then, I doubt it much exceeds 27mm in diameter.

Try sliding your glasses down your nose slightly to increase the distance until resting them on the flipped down eye cup is at the proper standoff distance.

The Arcturus ones are more or less self-centering. The ones with thumbscrews can push eyepieces off-center making merging more difficult. Baader Click-locks are not self-centering. They actually push the eyepiece to one side.

You could fit a 2" to 1.25" step ring into the eyepiece to allow for 1.25" filter use:

I have the APM Hi-FW 12.5mm and really enjoy using it. It's better in every respect than my Nagler T4 12mm (eye relief, lack of SAEP, etc.). Personally, I have never noticed EOFB in the APM. It's really bad in the 12mm NT4 by way of comparison. You might also check into the Founder Optics Marvel / StellaLyra LER UWA 14mm 80 degree. It is 2" only, but it gets great reviews.

Among affordable eyepiece pairs with near max true field of view for affordable binoviewers, I've used the 23mm Aspherics with my Arcturus binoviewer (made by Norin Optech), but much prefer the Svbony 20mm 68 degree UWAs for their much better clarity, contrast, and sharpness. They're best at f/12 and slower. I use the optical nosepiece of a vintage Meade 140 2x Barlow to reach focus. I just screw it into the insertion barrel of the BV.

Well, it's like having a minimum of 6 eyepieces in one, perhaps more if you dabble in half-mm focal lengths. So, that makes just over 2 pages per covered focal length! That doesn't seem so excessive then.😁

How long did you allow for acclimation? I see spiking with my 90mm triplet APO that looks like pinched optics for up to about 30 minutes. It eventually disappears after acclimation. Give your scope an hour to acclimate and check again.