Louis D

For me, I'd like to know how they compare to the vintage Vixen LV line since they usually come up for sale in the classifieds for around $70 each.  My 9mm LV views a bit dark, but is otherwise very similar to the Pentax XL and XW lines, just narrower.

Ecuador used to be a favorite of American ex-pats thanks to its almost perfect weather year-round in the capital Quito at 9350 feet elevation and in Cuenca at 8500 feet.  However, the cartels have recently started a turf war over control of Ecuador, so the homicide rate has shot through the roof. 

Nice report.

While the upper, positive, image forming part of the eyepiece may be quite similar to the Panoptic design, the fact that it has a negative, Smyth lens section down in the insertion barrel makes this a negative/positive design more along the lines of the 6mm and 9mm Redlines, just with much better SAEP control.

Based on your image of the bottom of the eyepiece, I'm pretty sure it has 7 or 8 elements just like the others in the line.  The 6 elements claim is probably just a typo.

Generally, eyepiece lines like the Radian, Delos, Delite, Pentax XW, Pentax XL, Baader Hyperion, Baader Morpheus, and many others with constant eye relief and field of view across focal lengths generally have similar, if not identical, upper image forming sections.  Only the lower and intermediate lens sections vary from focal length to focal length.  This rule of thumb tends to break down at 17mm and above in many eyepiece lines.  Even the upper section gets some redesign work done on it to get to lower powers.

Study these Pentax XL and XW lens diagrams to see what I mean:

On 30/04/2024 at 06:54, LukeTheNuke said:

Thanks, Louis. I'd consider a move to your side of the pond, but I'm pretty sure you wouldn't have me!

Nah, come on over.  We've been rolling out the welcome mat lately to anyone and everyone it seems. 😏

Too bad you're not in the US.  I just checked CN classifieds for Dobs under $3750 (roughly your budget), and I found loads options well below that price point including many custom built brands.  Hopefully you can find similar deals on your side of the pond.

A 77 pound mirror box in that StellaLyra 16" f/4.5 Dobsonian is quite a lot to solo hoist into its rocker base.  I can barely manhandle the 62 pound mirror box of my ~30 year old 15" Tectron into its base.

16 hours ago, LondonNeil said:

I'm confused.  Morpheus fov is 76⁰to the Hyperion 68⁰.

Nothing to be confused about.  Morpheus has wider AFOV while Hyperion has wider TFOV.  That's all.

12 hours ago, BlinneOrlaith said:

I've a good view at the house so hopefully the eyepiece is good for terrestrial viewing too. 

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.

29 minutes ago, Don Pensack said:

I find the APM 12.5 to have noticeable and objectionable edge of field brightening.

That's too bad, since otherwise it's fine.

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.

1 minute ago, DAT said:

Nice idea, had not thought of that. I am assuming thought that would act as a field stop and reduce the foc or am I talking rubbish? Either way, I think it’s a good option. Thank you

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.

3 hours ago, DAT said:

Actually I do, I swap from hovering over the lens to pressing against the eye cup. I just need to practice

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.

8 hours ago, DAT said:

Thank you, is that also known as the Orion LHD? I was hoping for a 1.25" to make use of filters I already have

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.

14 hours ago, Nakedgun said:

14 pages on this one eyepiece? 

Brother!

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.😁

On 17/04/2024 at 16:44, quasar117 said:

However, it was accompanied by flaring around the edge shooting off at symmetrical angles.

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.

35 minutes ago, Don Pensack said:

The Nagler Zoom has 5 elements in a 3 segment upper and 2 segment lower.

I kind of wondered if/suspected based on the 50 degree AFOV.

Has anyone discussed theories on the optical and mechanical organization of the Televue Nagler Zooms and the Svbony 3-8mm zoom?  My theory, they have a 4 element image forming positive group up top and a 2 element negative, Smyth, group down in the insertion tube.  To increase magnification, they simply move the two groups apart like a varifocal eyepiece such as my Speers-Waler 5-8mm "zoom".  This also maintains the size of the AFOV as in the S-W.  The mechanical trick to maintain near parfocality is to move the negative lens group downward during zooming in (higher power).  I have to do this with the focuser knob to maintain focus while zooming in with the S-W.

4 hours ago, Mr Spock said:

That isn't the finding of people who are using it. I find it just a little behind the 3.3mm TOE at the 3mm (3.5mm) setting.

On axis, off axis, edge, all?  At 3mm, it is very good across 70% of its field.  It's only in the outer portion it starts to fall apart in faster scopes.  I have no idea how well corrected the 3.3mm TOE is edge to edge.  Most folks only discuss on, or nearly on, axis performance of it and the Vixen HRs since few use these eyepieces for anything but planetary viewing or double star splitting.