Louis D

Did something similar with a $25 ebay 70-300. I had to remove a 35mm aperture stop behind the objective, remove the focuser, remove the objective lens cell, paint the interior of the tube flat black, put the lens cell back on, fashion a 2" drawtube focuser out of PVC plumbing parts and thumb screws I had lying around from other projects, paint its interior flat black as well, attach it to where the focuser used to be, put a 6" vixen dovetail on it I had lying around, and then put a 2" diagonal in it with a TSFLAT2 on its nose piece along with a widest field 30mm to 40mm eyepiece. Once I put about $500 of quality equipment around it and several hours of work, that 70mm achromat gives pretty nice wide field views for a $25 ebay special. 😆

Thomas M. Back did a really good job designing the 40mm TMB Paragon, and then it was sold under other brands without permission. The same thing happened to his TMB Planetary series. He designed each to be as good as possible at a particular price point. Apparently, he also designed the 30mm TMB Paragon. However, it is unknown who did the 35mm version's design. Did TMB design it but never release it under his TMB Paragon brand? Did someone else extrapolate the design based on the 30mm and 40mm versions?

You also have to watch out for "rust"/soft coating failure in some of the older Lumicon OIIIs:

To Don's list, I would add Meade 5000 HD-60 4.5-25mm : discontinued, but still some new-old-stock out there and lots of used, very good at 6.5mm and 9mm in particular with the 25mm a strong contender BST Starguider 25mm : Only one of the line usable with eyeglasses, but still not that well corrected Pentax XF 8.5-12mm : Field curvature can be bothersome for some Astro Tech AF70, also known as the Celestron Ultima LX, Olivon 70, Omegon Redline SW, Skywatcher SWA-70, etc.) 3.5mm to 22mm : VG at 22mm getting worse at shorter focal lengths Pentax XL 5.2-40mm : long since discontinued in favor of the XWs, but still pop up second-hand and still very worthy Meade 4000 UWA smoothie 14mm : An old favorite from the late 80s/early 90s Wide Scan III 80° 30mm clones : Surprisingly good in slower scopes at the edges, super sharp inner 40° in most scopes Meade MWA 26mm : Can get 78° with eyeglasses, but there's a lot of SAEP to deal with Baader Scopos Extreme/Orion Stratus 35mm : Baader recently sold out of NOS (I think I got the last one), but comes up used once in a while. Well corrected, great eye relief, super heavy. Meade 5000 Plossl 40mm : Most likely same optics as ES-62 40mm, but much cheaper on the secondary market. Super sharp in the inner 50% of the field. Vixen LV, NLV, and LVW : All discontinued, but all fine performers, and all show up regularly on the secondary market Celestron Regal 8-24mm Zoom : Hard to find, also sold with some Olivon spotting scopes (has a rubber grip instead of metal ribbing). Easily usable with eyeglasses once the twist-up eye cup is screwed all the way off (just keep twisting the cup down).

Generally none, but my 1990s Lumicon OIII will show the faint outer edges that blend into the sky-glow.

The 40mm Aero ED is well designed for it's price point. It would be unrealistic to expect Panoptic 41mm correction for 20% of the price. The 40mm Aero ED performs about as well as the 40mm Pentax XL, a bit worse than the ES-68 40mm offerings, way better than the GSO Super View, slightly better at the edge than the Vixen LVW 42mm, and better than the WO SWAN 40mm. The Panoptic 41mm is indeed in a class by itself correction wise, though. When you factor in weight, the Aero ED is a big winner for smaller scopes that are easily unbalanced. United Optics, ED 40 64 5 18 25 <5 12 20 Ast.,FC Pentax, XL 40 63.3 <2 18 28 <2.5 5 12 FC,Ast. Explore Scientific, 68 40 68.7 <2(5) 22 40 <1.5 7 13 Ast. +16% Explore Scientific, Maxvision 40 68.6 <3.5 25 40 3 8 12 Ast.,Coma,CA +15% GSO, Super View 50 48 <7 45 65 4 20 32 Ast.,FC Vixen, LVW 42 63 2 22 35 1.5 8 25 Ast.,FC +6% William Optics, SWAN 40 65 <6 >25 >35 N/A N/A N/A Ast. 5% Tele Vue, Panoptic 41 68 <2(7) 9 13 <2 6 8 Ast.,CA +17%

The 24mm APM UFF would be a good widest 1.25" field eyepiece with good eye relief for eyeglass wearers.

I think he uses a microscope of sorts with a reticle eyepiece to precisely examine the aerial image of the eyepiece. This allows for fairly accurate measurements of blur spots. The problem comes in with irregularly shaped blur spots. I get the impression that they're sometimes really diffuse or asymmetrical. He uses an artificial star to the best of my knowledge. He also tries to use them under the stars in actual telescopes as well to give his impressions of real world usage.

According to Ernest in Russia who tests many eyepieces on his optical test bench, the 35mm falls somewhere between the 40mm and 30mm. You can look on his summary page for United Optics, ED toward the bottom of the table. I've tried to repeat it below. The numbers reflect the size of the blur spot of an artificial star at center/70%/98% to the field stop using an F4 and an F10 lens. He moves the eyepiece to center the area of interest over the center of the lens image to eliminate lens aberrations influencing the results. The actual full report page is here. Try using Chrome browser to translate them. FL AFOV F4 F4 F4 F10 F10 F10 List of Eyepiece mm °/deg. centre zone edge centre zone edge rest aberrations United Optics, ED 40 64 5 18 25 <5 12 20 Ast.,FC United Optics, ED 35 70 5 20 35 <4 12 20 Ast.,FC United Optics, ED 30 66 5 20 40 <4 11 22 Ast.,FC

I'm guessing the manufacturer is just waiting for someone to pony up enough money for another full production run. These Chinese factories that supply the rebranding market don't generally start a production run unless they have a paying customer ordering a large enough quantity to make it worth their while. I've heard you have to order 300 to have you brand printed on them, but I don't know how many to actually restart a sold-out production run. I'm guessing well over 1000.

At 71° AFOV, if you concentrate on the center, the fuzzy parts are mostly in your peripheral vision where they are harder to perceive. I forgot to add my ~30mm line-up which includes the 30mm ES-82, 30mm APM UFF, and 30mm 80° WideScan clone. None of which will show as much sky (TFOV) as the Aero ED 35mm, though. The WideScan clone suffers mostly from massive field curvature which the cell phone camera suppresses with its depth of focus, so be aware it actually looks worse to the human eye which has less depth of focus. Make no mistake, it also has edge astigmatism, but it improves quite a bit by refocusing for the edge. If the design had a field flattening element or two ahead of the field stop, it would have a massively improved reputation.

The 35mm version has a 71° AFOV (and a 73° effective AFOV due to distortion) and a 44.4mm field stop by my measurements, so it comes pretty close to maxing out the field of view possible in a 2" format (46mm field stop). It should perform well enough at f/7.5 for your needs. The 40mm Maxvision/Meade 5000 SWA has the same optics as the 40mm ES-68, so if you can find one used, it's an excellent choice. It is much better corrected in faster scopes, but also much heavier (30.8 ounces vs. 12.3 ounces for the Aero ED). Below is comparison image of my widest field eyepieces taken through a field flattened f/6, 72ED refractor. It should give you some idea of the relative edge correction characteristics of various eyepieces. The 40mm Meade 5000 Plossl is basically the same as the new 40mm ES-62. The Baader Scopos is discontinued.

It does work fine with glasses in my experience. I think it just slipped Don's mind. He uses one with glasses, so that's about as much proof as I need. I found the 17mm and 12mm NT4s to also work with eyeglasses, but they had such finicky exit pupils once the field stop popped into view that they were too tiring to use, so I replaced them with the ES-92s.

The nebula colors tend to remain similar (still pretty much gray), but the surrounding star colors get a wonky red/green color to them that some people find very distracting.

Carefully clean off all face grease from the top of the eyepiece, generally a folded down eyecup, and you won't have this issue. I never swap between glasses on and off with the same eyepiece because I know I'll get smudged eyeglasses.

Try putting anti-vibration pads under each tripod foot to reduce vibration dampening time. It won't do anything for slop in the mount or focuser, though. Try shining a bright light on a white piece of paper and stare at it for a while to activate the cones in your fovea and to constrict your iris before looking at Jupiter. It might help decrease the image blow-out you're seeing.

And ZAOs at the short end along with Zeiss surgical microscope eyepieces for binoviewers. There are even the unobtainium Zeiss professional observatory monocentrics of which only a handful were made and delivered to observatories many years ago.

There's the new SVBONY zoom eyepieces getting a lot of chatter on Cloudy Nights these days. All seem to be well thought of according to early adopter reports. They're available in 7-21mm, 8-24mm, and 10-30mm focal ranges via ebay, Amazon, AliExpress, and the SVBONY website. The 8-24mm is probably going to have the best eye relief for eyeglass wearers. It's uncertain how much additional true field of view you'd gain going with the 10-30mm over the 8-24mm. Neither is going to be particularly wide at the long end.

@John Have you noticed any eyepieces or telescopes presenting out of focus edges that used to be in-focus? This happened to me and my 14mm Pentax XL. I had been using it for well over a decade when I noticed the edge didn't focus at the same point as the center about 6 years ago. That was also about the same time I had to start wearing bifocals and computer glasses full time. I was perplexed by how I had never noticed it before until I realized it was my eyes that had been compensating for the FC all those years. I was a bit crushed realizing what I had lost. Now I had to use flat field eyepieces in flat field scopes.

Photographic ND filters are rated by stops of darkening. Thus, an ND13 should pass 1/(2**13)=1/8192 of the original light. These are typically used for solar imaging. A mislabeled ND filter could be very dangerous.

Because it depends on your visual accommodation. If your eyes are young, FC is not a big deal. If you're old and suffering from presbyopia, it becomes an annoyance. People really need to specify whether or not they suffer from presbyopia before commenting on FC. This is true for both eyepiece FC and telescope FC.

Yeah, I don't think so on the 22mm NT4. 🤨 It took me years to find one for $260 shipped. I had been using the 22mm AstroTech AF70 quite happily for years before that. I was thinking the wife would like to have a scope to look through while you're locating targets in the Edge HD. Heavy eyepieces do tend to want to make a 72ED turn turtle. You have to rig up a counterweight at 90 degrees to the scope to counteract the heavy eyepiece at higher altitudes. Otherwise, the eyepieces work well in the 72ED. You will notice field curvature due to the short focal length. I ended up adding a TSFLAT2 field flattener to the front of the 2" diagonal to flatten it out. The other issue is you have to have an altitude lock on the mount to keep the scope on target during heavy eyepiece swaps.

Focal extenders don't increase magnification very much with increasing working distance, so they would tend to continue to yield their rated magnification when used ahead of a binoviewer. Since they are made up of two sections, the negative Barlow section below and the positive section above it to parfocalize the diverging rays, the nose piece alone would most likely be negative only. I would try it as-is ahead of the binoviewer.

I have the 22mm Nagler T4 as well. It's very nice, but a bit tight on eye relief compared to the others you have listed. If you can pick up one used for about $300 equivalent, it's a good deal. You'll find you'll either leave the Powermate in or out, but not continuously swapping it. Thus, it's not really that useful for filling gaps. The 17.5mm Morpheus is another option if you want to stay light and less expensive. I've thought about picking up one for this reason. I still recommend budgeting for a 72ED on an alt-az mount for 11x to 62x powers. I really enjoy cruising star fields and observing clusters and asterisms that are too big for long focal length scopes.

I couldn't handle my 14mm Pentax XL's field curvature once I got presbyopia, so I replaced it with a 14mm Morpheus that has way less. It's not quite sharp in the outer 15% of the field due to slight astigmatism and field curvature, but it's much more engaging with its measured 77° AFOV. I've read that the 14mm XW suffers from the same field curvature as the 14mm XL, so you have to weigh that if your eyes are fixed focus. That said, I rarely use any 14mm eyepieces because my 12mm ES-92 is so much more engaging than any of them and covers a larger TFOV. I have thought about trying the Hi-FW, but it would be a niche player for use when I want to strictly stick with 1.25" eyepieces.