Don Pensack

If you have a Moonlite focuser, use only 2 screws to tighten something into the focuser--remove the 3rd screw and keep it in you spare parts kit. Screw 1 presses against the other side of the drawtube but allows wiggle. Screw 2 presses against the other side, making a 3-point contact--no wiggle possible. Screw 3 presses the inserted accessory away from the drawtube wall, which is a negative for accurate registration. This is because the 3 screws are at 120° apart.

Ernest Maratovich (apologize if name spelled wrong) has measured the Morpheus at: http://astro-talks.ru/forum/viewtopic.php?f=32&t=1483#p41976 4.5mm--78° 6.5mm--79° 9mm--78° 12.5mm--78° 14mm--78° Within the margin of error, that matches Louis' figures. The weakest one at the edge at f/10 is the 12.5mm and 14mm, but, based on his figures, essentially perfect. At f/4, the14mm is worst. in my coma-corrected 12.5" f/5.75 (the CC-corrected f/ratio), even the 14mm is pinpoint at the edge and a star stays point-like past the field stop. I've used these in scopes from f/3.45 (CC-corrected) to f/8 (refractor) and would say their "critical f/ratio" is about f/4.5 and that they are not well corrected below that f/ratio. So the f/4 figures don't indicate flaws in the eyepieces, merely their use at too short an f/ratio for the design. In other words, not the best design for the ultra-fast scope. As for effective eye relief, the eyepieces in question are all usable by me with glasses on. If wearing glasses, what do I have to do to see the field edge? These are all just compared on my 4" apo on a distant land target: 17.5mm Morph--glasses 2mm away from rubber, MFR eye relief 23mm, maybe 20mm effective 14mm Morph--glasses touching rubber, pressure light , MFR eye relief 18.5mm, maybe 17.5mm effective (pressure compresses the eyecup) 12.5mm Morph--glasses just touching rubber, no pressure, MFR eye relief 20mm, maybe 18mm effective 30mm APM--glasses just touching rubber, no pressure, MFR eye relief 22mm, maybe 18mm effective (top lens recessed a couple mm) 22mm Nagler T4--glasses touching rubber, pressure moderate, MFR eye relief 19mm, maybe 17mm effective 20mm Pentax XW--glasses touching rubber, pressure moderate, MFR eye relief 20mm, maybe 17mm effective It took me a while to realize exactly how much eye relief I actually needed to see the entire field of view in an eyepiece with glasses on. And, I suspect like many glasses wearers, I don't really need 20mm of "effective" eye relief--17 to 18mm will do. The only figure where I disagree with Louis is the eye relief of the 30mm APM. I couldn't see the entire field at 16mm effective eye relief, yet it's easy to do so. Hope those impressions help someone looking for a long eye relief eyepiece. I should note I have fairly deep-set eyes and the distance my glasses are from my eye exceeds the width of my little finger, so those whose glasses sit closer to the eye might find all of those eyepieces to have even more eye relief than I found.

Touché. However, I have more than one scope and it is the same in the other scopes which do not use a Paracorr. They do, though, use brass split ring binding systems. I need to investigate other types of binding and compatibility with my focusers, though. Maybe a Twist-Lock diagonal.

I see you have your thinking cap on. ES gave that some thought, too, and used stainless steel for the ring instead of brass. Much springier. My immediate cure was to remove the brass split ring and use delrin screws to press directly on the eyepiece barrel. And to use a focuser drawtube with a smooth bore that has no brass split ring in it. There is a cure with leaving the brass split ring in place, and it is a sanding of the split ring so its cross section is not || , but (). I did that for a customer a couple years ago and it solved his problem. But some eyepieces hang up on the top lip of the Paracorr, above the groove where the split ring resides. Only a smooth internal bore on the top would solve that problem. It just shouldn't be this much work to remove an eyepiece.

No, because all 4 of the eyepieces with problems are 2", so no adapter is used, and a Paracorr resides in the focuser 100% of the time. The Baader Click Lock adapter isn't a cure, since it has an undercut on the outside, so it's no better than the TeleVue adapter. Several other adapters have smooth sides and work great with the Paracorr, but the 6mm and 8mm Ethos need a "Hi-Hat" style adapter to safely use them as 1.25" eyepieces, which means the TeleVue Paracorr adapter. I could use a Twist-lock, smooth-sided, adapter for the 9mm, 12.5mm, 14mm Morpheus eyepieces, but the 17.5mm needs an in travel adapter, and I draw the line at 2 different adapters, not 3. Plus, they work fine in the Paracorr adapter since they don't have undercuts. I am leaning toward attaching 2" adapters to all the 1.25" eyepieces and just using them all as 2". I would need a number of adapters, but it could be a permanent fix.

Unfortunately, where you have positioned your rings means that in some focusers and adapters and star diagonals, the thumbscrews will press on the edge of the undercut and probably tip the eyepieces. There is a cure for that, however: add barrel extenders to all the eyepieces and place the parfocalizing rings in the middle of the undercut. You could keep all the eyepieces parfocal that way, albeit at a somewhat inward movement of the focuser.

The amount the Parallizer is shoved sideways in the focuser matches the amount of sideways movement the other way by the thumbscrew in the Parallizer, so it is centered. I wrote some illustrated instructions for the use of the Parallizer. The Howie Glatter Parallizer.docx

Some, but not all, eyepieces or accessories with undercuts are a problem and some aren't. My Paracorr's adapter was incredibly hard to remove from the Paracorr if tipped even an extremely small amount, which proved to be a sure thing in the field. The 2" eyepieces were not hard to insert or remove. Neither were 1.25" eyepieces in the adapter. But that adapter would sometimes need a lot of wiggling and pulling to get it to come out, even with the thumbscrews backed out all the way. I filled in the undercut with metal tape and the problem simply disappeared. Inserting and removing is now a matter of one second and there is no catching going in or coming out. That is the difference a smooth barrel makes. You guys who have no problems with undercuts are lucky--you just haven't gotten one of the problem fits that would cause you to curse. I remember back when no eyepieces had undercuts, and inserting and removing eyepieces was incredibly easy. You loosened the thumbscrew 1/32 turn and out slid the eyepiece. Now, you do the same and, in the process of pulling the eyepiece out, it catches. So you loosen the thumbscrew(s) some more, and try to remove the eyepiece and it STILL catches. Now you've unscrewed the thumbscrews a full turn or more and the eyepiece STILL catches. Finally, you loosen a screw so much it falls out on the ground and the eyepiece is still stuck. So you wiggle it back and forth a lot and you finally find a point where the eyepiece forces the brass split ring back in its groove and the eyepiece starts sliding out, only to catch a tad on the opening of the focuser as the bottom of the safety groove catches on the lip at the opening. I don't know why, but I always seem to get those problem children. It's no better when inserting the eyepieces, either. They tend to bump and slightly catch going in as well. 4 of my 12 eyepieces have undercut grooves (8 don't), and those 4 are always a problem putting in or taking out. Here is something interesting: The Paracorr has a smooth side without an undercut. But the inside of the top has 4 grooves an eyepiece can bump on going in. And though the 6mm and 8mm Ethos eyepieces have undercuts in their 2" skirts, their 1.25" barrels are smooth. And, used as 1.25" eyepieces, they slide into and out of the adapter without issue. I feel like Job. My life has been filled with wars, economic chaos, a pandemic, cancers, and injury. I just want to live out the few years I have left without the plague of undercuts on eyepieces.😆

Unfortunately, there are a lot of 1.25" eyepieces that don't work in the Parallizer adapter. If the upper barrel protrudes sideways enough to stick out beyond the adapter, the eyepiece hits the thumbscrew, which is angled up at a 45° angle. There is at least one person here who machined off the top of the Parallizer to make it flat and installed his own thumbscrew 90° to the bore. If the eyepiece does not hit the thumbscrew, though, there is no better adapter.

No, it's not a collet, merely a mechanical way to press the brass split ring into the eyepiece.

Interesting. My wedding ring is made from Silicon Carbide and is heavier than gold. I have a couple other rings made from titanium and they, too, have a high polish. There are a lot of materials that eyepiece barrels could be made from, but aluminum is still the most practical because of low weight and low cost. Speaking of lightweight, imagine beryllium or magnesium as a material--talk about light.

Possibly, since only 300 were made (no economy of scale). It points out that a dual-size eyepiece should have a removable skirt if the eyepiece can be used as a 1.25".

Stainless steel doesn't have that shiny chrome look, though. The Stellarvue Optimus eyepieces do have stainless steel lower barrels, and they are not unique. However, as a result, they are a lot heavier than the all-aluminum APM versions of the same eyepieces.

There are a number of smooth-sided adapters out there, some of which don't require the slit in the focuser like the Moonlite. The new 7mm APM XWA eyepiece has a threaded on 2" adapter with smooth sides, and the 1.25" barrel underneath is also smooth sided. But that could be done because it was a new eyepiece and was ordered that way.

The tapered edge to the bottom lip of the undercut was several years ago, though I couldn't tell you exactly when. They did so to get the eyepiece to remove a little easier by shoving the brass split ring aside on removal and to get around the lip above the brass split ring. TeleVue lower barrels have been chrome plated brass for a long time, and chrome is usually put on top of nickel to adhere better. Nickel will dull with time, and, if the chrome plating is very thin, may cause the surface to dull, perhaps irregularly. You might try a little jeweler's polishing rouge (aka Simichrome polish) to buff it up if you want. TeleVue said that they had a few reasons for not wanting to offer smooth barrels for the eyepieces as an option: --the barrels were expensive--about $50 at their cost in the volume they contemplated --a large number of different barrel sizes and shapes --they didn't have enough manpower in the office to do the switch--especially if it proved popular --it would be a marketing admission that not everyone liked the undercuts --it might result in more damaged eyepieces, which could tarnish their reputation (though, I would argue, not any more than the undercuts in the first place) Reasons 3 and 4 are why they couldn't switch back, either, in addition to: --making old stock, a lot of which is at the dealers, obsolete or less desirable --meaning they would have to have double inventory if the smooth barreled versions came from the factory, which they couldn't afford --meaning the dealers would have to carry dual inventory as well if some people preferred the undercuts (and some people do). So, we aren't going to see the disappearance of undercuts in eyepiece barrels. But at least an attempt was made to modify the undercuts to make the eyepieces easier to remove. That still leaves the incompatibility problem. Brass split rings, collets, et al. are designed to hold smooth barrels securely. Undercuts (cylindrical or conically tapered) are designed to work best with thumb screws. If you see the issues, then you can do what I did--simply use thumbscrews and leave marks (or use nylon or nylon tipped thumbscrews), or look for smooth barrels (not many of them, though).

Sorry, the only point was that comparing discontinued eyepieces for edge sharpness that are not available for purchase is useful information only to the purchaser of used eyepieces. You're right, though, that there are probably 17mm Naglers still in stock at various places, and that the 17mm Astrotech is available under other labels.

That's great, because the collet comes up all the way to the opening of the orange aluminum. It needs to grab the skinny little 1.25" section above the eyepiece's undercut to properly align the eyepiece with the bore of the adapter, and on that one it does. On this one, also, the internal collet comes up all the way to the opening: https://www.cloudynights.com/topic/182290-new-redesigned-twist-lock-adapter-from-antares/ The Celestron one is very close, though: https://agenaastro.com/celestron-2-to-1-25-twist-lock-eyepiece-adapter-93668.html Some collet style adapters do not, so they can tip: https://www.highpointscientific.com/baader-clicklock-2inch-to-1-25inch-adapter-t2-15b?utm_source=google&utm_medium=cse&utm_term=BAD-T2-15B&gclid=CjwKCAjwmqKJBhAWEiwAMvGt6AskBk8OqRTcxNGFBH7EoNEHB3a3oJr9vtaDY0obQwvjOTP1qLrtfxoCFi4QAvD_BwE With that one, the fit depends solely on tolerances of fit of barrel through the opening.

The answer to your question is yes. The small 1.25" section at the top is necessary to be inserted in the focuser so the eyepiece doesn't tip. And your assumption about Click-Lock and Twist-Lock attachments is correct.

TV looked into this and over a decade ago the barrels were about $50 apiece at TeleVue's cost. Then there is the labor of changing the barrel. This might be a solution for a machinist who can make his own, but it's not commercially viable.

All those eyepieces are discontinued except the ES.

I can't say because I don't know your scope. In an 8" f/6, the 25mm..12mm..8mm..5mm can be a fairly complete set. In a 102mm f/7 refractor, the same 4 work out fairly well. In an 8" SCT, though, you need something longer than 25mm as a low power, and 8mm might be a highest normal power eyepiece. There, a different brand of eyepiece might do better.

If the undercuts are somewhat of a problem in your equipment, then filling the undercuts with metal tape is an easy fix, and it can be undone to sell them. Personally, I prefer smooth barrels and a focuser drawtube that is smooth with no compression ring or collet, just thumbscrews to tighten down on the inserted item. It leaves marks. Oh, horrors? Who cares? I don't buy eyepieces thinking I'm going to resell them anyway. The newer tapered edge undercuts TeleVue uses are less of a problem than the earlier sharp-edged ones. The conically-tapered undercuts on a lot of recent eyepieces (ES, et.al.) are a real problem for the split ring binders found in most focusers and star diagonals. The metal band is twisted, often permanently, by tightening down on the slanted surface. ES went to stiff stainless steel split rings instead of brass in their focusers and star diagonals. Collets (as in many adapters) that tighten uniformly around the perimeter can solve some undercut problems, but they don't tighten on the barrel at the bottom of the undercut and, if they are the type with small metal rods, can actually get caught in the undercuts. However, face facts. Almost no modern eyepieces lack undercuts of one sort or another, so limiting your purchases only to smooth barrels is only hurting yourself. So figuring out how to deal with undercuts is part of the hassle of using contemporary astronomy equipment. I deal with it by filling the undercuts with metal tape, eliminating the split ring binders (remove them if they're there) in favor of thumbscrews or collets, and having a few eyepieces without the safety undercuts and using a focuser with a smooth bore, a combination of all 4 solutions. I had one adapter that had an undercut that always caught, and it had a tapered cylindrical undercut. I taped it and it slides in an out without issue. So I wouldn't remove the tape if its presence make the item work well. You might regret it.

Get the Starguiders. The wider, more open, apparent fields are well corrected and more enjoyable to use for general viewing.

https://www.lifehacker.com.au/2014/08/whats-the-difference-between-a-reticle-and-a-reticule/ https://www.yourdictionary.com/reticule https://www.collinsdictionary.com/us/dictionary/english/reticule https://www.merriam-webster.com/dictionary/reticule https://www.lexico.com/en/definition/reticule My dictionaries in the house refer to the drawstring bag first and a variant spelling of reticle second. Spellings are listed as variant, the index states, when they are not as common and are used, usually, only in specific geographical areas. I at first thought this must be a British spelling, like colour/color or honour/honor, but the dictionaries convinced me otherwise. It is possible, I speculate, that reticle became the dominant spelling to differentiate it (and avoid confusion for the reference) from the word reticule used commonly to describe a bag.

No, most of those big scopes, if ever used visually, use 4" or larger eyepieces of 80mm and longer focal lengths. In the 60" at Mt. Wilson, a 50mm eyepiece is 488x.