Louis D

Especially because it avoids the 25% "special" US tariff on products from a certain country I won't name here. And, if you stay under $800, there's no US import tariff due to the de minimus daily personal exemption. That, and I've yet to see a non-US dealer collect and remit US state sales tax like Euro dealers expect US dealers to do for VAT. Taken all together, it can often more than pay for the cross-pond shipping costs. On eyepieces with low shipping costs, it's often a no-brainer to cross ship.

By all accounts, the 16mm NT5 is exceptionally sharp, but with only 10mm of eye relief, fairly tight even without eyeglasses. The entire T6 line was designed with 12mm or ER because that seems to be the Goldilocks amount for non-eyeglass wearers. They've become the 82 degree gold standard against which all other UWAs are judged. Here are some eyepiece tests of the Tele Vue eyepieces you're interested in from Ernest. You'll need to translate them using Google or their Chrome browser: Panoptic 24 mm Nagler 16 mm Type 5 Nagler 13 mm Type 6 Nagler 5 mm Type 6 Overall, he liked them a lot. Here's the table with links to fixed focal length eyepiece tests/reviews. Here's the table with links to zoom eyepiece tests/reviews.

Or, if you get the American-spec Skymax with the 2" visual back or make the mods yourself as I did for my Orion 127 Mak: The difference isn't quite so drastic. Sure, there's about a 40% falloff in illumination, but I find it works quite well visually. This is a comparison image through the 127 Synta Mak: You can see how the 2" Meade SWA (ES-68) 40mm gets darker due to vignetting center to edge thanks to the 27mm diameter rear port throttling the 46mm field stop.

I finally found a reasonably priced, used Tele Vue Nagler T4 22mm and have been using it at that focal length. Before that, I used the Astro Tech AF70 22mm which is the same as the Omegon Redline. It is also 2"-only. It's very well corrected except for the last 5% of the field that has a bit of astigmatism in fast scopes. It also has enough eye relief for eyeglass wearers.

Correct. Spherical Aberration of the Exit Pupil (SAEP). Basically, not all exit rays across the field of view come to a single point above the eye lens. Read this post of mine to see some nice animations from @Ruud explaining the different shadow types: SAEP shadows are in the middle of the field, not the edges. That same thread has some images I've taken showing the extend of SAEP in various mid to long focal length eyepieces. To get the ring shadow, the camera has to be exactly level and on axis with respect to the eye lens. Otherwise, you get the classic kidney-bean shadow to one side or the other. A few even show Chromatic Aberration of the Exit Pupil (CAEP) with rainbows. CAEP is caused by different wavelengths converging at different distances above the eye lens. It's often referred to as the "Ring of Fire" effect. Small, extended objects like Jupiter near the field edge actually split into spatially separated red and blue images in my experience.

A bit off topic: Seeing the recent thread on choosing a 4" refractor for visual (Choosing between 4" ED Refractors for visual), and having just compared my 90mm APO to my 150mm Newtonian, just exactly how much improvement would I see going up 10mm to 12mm in aperture to a 4" ED or APO refractor over the 90mm APO triplet? Would that little extra bit of aperture reveal the Trapezium E component that the 90mm simply could not even hint at? Should I instead jump to 120mm or 125mm for my next ED/APO?

I've found the SVBONY 68° Ultra Wide Angle 20mm works exceptionally well in my barlowed binoviewer at f/18. They're light, compact, have enough eye relief for eyeglass wearers, have a decently wide field of view, and are inexpensive. See my full take on them in this mode below:

I find the well figured, ultra wide field, long eye relief 20mm to 26mm region to be rather skimpy at any price. There's the 20mm SL/FM, 22mm NT4, and 26mm Meade MWA. The MWA has excessive SAEP (and is discontinued), the NT4 has some SAEP, and I have no idea about the SL/FM and SAEP. I'm holding out hope that ES expands the ES-92 line upward to 23mm or so.

For the £10 difference, I would definitely go for the Founder Marvel Ultra Wide 14mm over the StellaLyra 14.5mm 1.25" 68º LER / WA. It will have a wider field, better correction, and similar eye relief with the eye cup screwed down. Definitely worth trying Don's rubber band (O-ring) trick if you need the cup up higher to avoid blackouts. You could also make an adjustable eye cup by wrapping black crafting foam around the outside of the eyepiece, cutting to circumference, and then gluing the ends together. It could be slid up and down for adjustment. Another option would be to stack a 43mm to 49mm step-up ring on a 49mm to 50mm step-up ring onto the eye cup thread if it is indeed 50mm x 0.75mm threaded. You could then thread a 43mm Morpheus eye cup onto the 43mm step ring thread.

The big three Dob makers are Synta (Celestron, SW, and Saxon), GSO (SL, Apertura, and Bintel), and JOC (Explore Scientific and Bresser). I would look for a local ES dealer to compare a third option. The GSO ones generally have the most features out of the box while the ES have the best altitude axis (true trunnions). Synta's Celestron Starsense Explorer app has been well received, but the scopes themselves are unremarkable with antiquated 2" focusers. They generally require the most tinkering. Make sure you see how big a 12" Dob is in person before buying one. They can be quite an armful. You might consider a truss tube over a solid tube at 12".

So, let's say you're set at 40x for your lowest power and largest exit pupil (30/6 = 5mm) with the APM UFF 30mm. Based on my observing preferences after 25 years, my next step up in power would be 70x to 85x, and a 2mm to 2.5mm exit pupil for general DSO observing. This would be an eyepiece range from 14mm to 15mm to satisfy both criteria. I would say to give the 14mm Morpheus a try. It comes with an eye guard extender if you need back off from the eye lens a bit.

Just like the Zeiss Abbe Orthos (ZAOs). I've seen complete sets advertised for $5000.

How about the 13mm APM HDC-XWA 100° and other brandings by the same manufacturer, if you don't need long eye relief? Apparently, they're lighter than the competition while still having excellent correction. There's also the 12.5mm APM Hi-FW and its Sky Rover stable mate if you need long eye relief. Don dislikes its EOFB, but I've yet to even notice it. Perhaps if I observed under truly dark skies I'd notice it. I find it to be very well corrected. The 12.5mm Morpheus is also well liked if you need long eye relief. I don't have it, but I do have the 14mm Morpheus and find it very good, with just a bit of astigmatism in the last 5%, although Don reports there being none. Perhaps I got a dud. I measure 78° on it, so just barely narrower than the 14mm SL 80°, but in a 1.25 barrel. I really like the 12mm ES-92, but it is very large, heavy, and expensive. You might struggle with eye position with it. Ironically, I've measured the 12.5mm Hi-FW to have a slightly larger field stop than the 12mm ES-92 despite the former being in a 1.25" barrel and the latter in a 2" barrel. They have opposite distortion as well. The ES-92, like most astronomy eyepieces, stretches objects toward the edge while the Hi-FW compresses them. People rave about the 12.5mm Noblex and 12.5mm/10mm Nikon NAV-HW, but both are very expensive. There's also the 11mm Tele Vue Apollo if you can find one used and afford it. I believe the limited edition production run ran out. There are lots of excellent options between 11mm and 14mm.

The US version comes with a 2" visual back, diagonal, and 28mm eyepiece.

If you strictly use it with a 1.25" diagonal and lightweight eyepieces, you should be fine. However, 2" diagonals will leave the focuser with very little infocus travel left. Heavy eyepieces with a 2" diagonal may cause the draw tube to slip at high angles as well.

Best not to go down this rabbit hole any further to avoid this thread being locked for being too political.

Don't Leica, Zeiss, and Swarovski still make some eyepieces in Europe for their spotting scopes? They can be adapted for astronomy use.

I don't know about European optical companies, but US ones will always have DoD contracts to fulfill for the US military. That's what keeps Vernonscope afloat.

Could there be a promotion/relegation in the works?

When using the 3-8mm zoom last night, it dawned on me where I had heard that same mechanical sound at each detent. It is the sound of my optometrist's phoropter as it changes lenses. Since I consider those to be precision optical equipment, I think that's a pretty good achievement for the zoom to sound the same. They certainly did not cheap out on the mechanical side of things.

I am not familiar with that Newt, so I did a quick search and came across this thread on CN of someone using it for imaging. It sounds decent, but the price is pretty steep for a 6" f/5 Newtonian with some issues that needed to be ironed out. Hopefully, TS has resolved the issues the OP had in 2018.

Just got back in from a couple of hour comparison of the two scopea on Jupiter, Collinder 70, the moon, the Orion Nebula, and the Trapezium. First, both make for excellent scopes. I could see someone being quite happy with either, especially not having both to compare views. The differences were more subtle than I expected. Both are pretty much color free. The atmosphere was causing a bit of red/blue fringing top to bottom on Jupiter and the moon in both. Before it got reasonably dark when observing Jupiter, the central obstruction shadow of the Newt was really annoying. Huge win for the unobstructed APO for daytime use. Jupiter: Better image scale at the same exit pupil made it easier for me to see past my floaters at a particular magnification. Aperture wins. As I increased magnification, the APO didn't really decrease much in contrast on the belts. However, no new details were visible. The Newtonian definitely had reducing contrast meaning lower powers were better. Unobstructed wins. Perceived details seemed better on the edges of the belts in the Newt. They appeared frayed instead of solid as in the APO, as if some detail was about to appear with a bit more aperture. Aperture wins. Collinder 70: Pretty much dead even. The APO's stars looked a bit more pinpoint, but the Newtonian showed dimmer stars a bit better. Tie Moon: Looks great in both. Perhaps a bit higher contrast in the APO, but a bit finer details visible in the Newt. Tie Orion Nebula: More nebula brightness, extent, details, and contrast visible at all magnifications. APO didn't really show anything as good. Aperture wins. The Trapezium Stars were possibly a bit more pinpoint in the APO, but the Newt was no slouch. Tie E component plainly visible in Newtonian, but no where to be seen in the APO. It was not a subtle difference. Huge win for aperture. Overall, I preferred the larger exit pupil at a given magnification in the Newt due to my really bad floaters. At really small exit pupils in the APO, I can even plainly see the shadow caused by my observing eye's vitreous humor detachment. It wasn't as obvious for some reason in the Newt. I confirmed what it was because it wasn't there in my non-observing eye which has no detachment. Basically, the higher contrast of the APO just could not compensate for the extra aperture of the Newt. The higher position of the focuser in the Newt was also easier to use standing instead of crouching as with the APO. When using the APO alone, I extend the tripod legs to avoid crouching which leads to longer vibration settling times. The APO's focuser tends to unravel with heavy eyepieces at high altitude angles unless I tighten the drag adjustment. The Newt's focuser doesn't seem to have this issue, probably because of its angle relative to the ground. Size wise, they're about the same length with the diagonal attached and the focuser extended to its typical position on the APO . The Newt is obviously wider. The Newt is also a few pounds heavier. Ignore the laser sight on the Newt. I forgot to take it off for the picture. Yes, the APO is more svelte looking. My grown son says it looks "legit". The Newt looks kind of chunky in comparison. As for Sir Patrick's assertion about the 3" refractor versus the 6" Newtonian as applied to modern scopes, I'd say "it depends". Does slightly higher contrast and daytime use matter most? Does light gathering and resolution matter most? Size-wise, there's not a lot to distinguish between them.

You read the wrong line off of Ernest's report: Light diameter of the field lens, mm 44.6 The field stop diameter is as follows: Light diameter of field clearance* 1 star, mm 41.2 I measured 41.0mm for the field stop, so the same within the margin of error. That also puts it at the same field stop within the margin of error as the 25mm ES-100. The field lens of the Meade is larger than the effective field stop. I suppose eFS is just as fictitious of a construct as eAFOV when you think about it. It simply makes using the standard TFOV calculation easier than using the physical field stop diameter and accounting for the magnification distortion effect of the Smyth lens. You're right, you see 100° in the ES and 83° in the Meade, but the same true field of view in both at the same power (at least in the center). eAFOV is simply another way of stating the field stop for comparing TFOV. The Meade's SAEP is not bad as I'm finding out if I view at 17mm to 18mm of eye relief and live with the resulting 79° AFOV which is very similar to most Morpheus eyepieces at 78°. That's a loss of only 4° AFOV which I can live with. What is the AFOV at 17mm to 18mm of eye relief with the 25mm ES-100? Is it only 4° less than at the design usable eye relief? If it is, I may consider buying one.

As a follow-up, I had the 26mm Meade MWA out a few nights back. I think I've made my peace with it three years later. For an astigmatic eyeglass wearer, it views like a 25mm Morpheus would in many respects, but with compressional distortion at the edge instead of expansional distortion. As such, the moon gets squashed instead of stretched as it approaches the field stop. It is surprisingly well corrected over the vast majority of the field of view, certainly the portion viewable without scanning around the field by swiveling your eye. It provides a nice boost in power over the 30mm ES-82 while maintaining almost the same true field of view in the "Easy View" mode. I tried to see that last few percent of the AFOV, and was thwarted once again by SAEP. You simply can't see more than a fraction of that additional field at one time. Other parts will go dark to see to the true field stop. I'll try to get it out more often now to make more use of it. The more I use it, the better I become at working around its limitations. Of course, if ES came out with a 25mm ES-92 as good as the 12mm and 17mm versions, I'd ditch the Meade in a heartbeat. 😄

That's pretty much my experience with my 127 Mak as well. I've only seen festoons and barges clearly starting at 8" of aperture (needs to be exceptionally well corrected and acclimated), becoming blatantly obvious by 12" of aperture in an exceptionally well corrected scope on nights of exceptional seeing. If collimation, figure, polish, seeing conditions, etc. don't all align, fine, low contrast details will turn to mush guaranteed. All you can do is buy or make the finest scope you can, use the best eyepieces possible, get yourself to places with the best seeing conditions, wait for opposition, make sure everything is well collimated and aligned, and then hope for the best if you want to see low contrast details on Jupiter. When everything does align, it's hard to stop taking in the view because it's so mesmerizing to see such detail. It's quite sublime. Mars is the same way, except that dust storms on Mars can ruin our best laid plans here on Earth.