Louis D

Ideally, wouldn't you want the finder scope directly opposite the altitude pivot point (the side facing the camera)? Where it is in the image will make it turn turtle once the altitude gets high enough, unless you crank down on the friction knob.

I know, but still, we can dream someone got a hold of a T7 prototype (or the mythical T3).

The BHZ has a 44° AFOV at 24mm while a 32mm Plossl generally has a 52° AFOV. Assuming minimal magnification distortion, you're going from about 0.7° to 1.1° TFOV on the sky in your 127 Mak. That may not seem like a lot, but it is a 2.5x increase in area on the sky seen in the image circle. In the States, Synta is shipping these 127 Maks with 2" visual backs and 2" diagonals. I did the same upgrade to mine before this became standard here. With a 40mm, 68° AFOV eyepiece, it increases the view seen on the sky from 1.1° to 1.8° (or 1.0° to 1.7° using field stop measurements). That's another 2.7x (or 2.9x by FS) increase in area on the sky seen in the eyepiece. Relative to the BHZ at 24mm, that's a whopping 6.6x increase in area on the sky seen in the eyepiece. Yes, there is about a 40% decrease in illumination in the outer field of view, but it's hardly noticeable when looking in the center. The difference in what can be seen in the eyepiece is enormous, especially for rich star fields. Below is the difference demonstrated by photographing a ruler through both a 24mm widest field eyepiece (roughly the same field stop size as the 32mm Plossl) and a 40mm widest field eyepiece. You can see how it gets dimmer toward the edge. And here's how it looks in the focuser from two different angles:

I know I'm not going to mess with the near perfect factory collimation of my 127 Mak for BV usage. It works well enough as-is for my purposes.

You could start by reading this mini-review of the Orion equivalent by Tom Dey (a retired optical designer) on CN.

But that requires one on each eyepiece if you don't like moving them between eyepieces. Also, they don't do well if you tip your head to look at the edge of ultra to hyperwide eyepieces. The cylinder corrector needs to be perpendicular to your eyeball, not the eyepiece, so correction is best only when looking at the dead center of the view. Lastly, you still need to put your glasses back on to look up at the sky if you're in the object hunting phase. For all these reasons, I stick with a dedicated pair of distance corrected eyeglasses with the lowest index material possible to minimize CA. I'd get them made in glass if I could locate a place still willing to do it.

It also depends on how fast your scope is. Orthos tend to have poor edge correction below about f/8. If you have an f/5 or faster Dob, you'd really notice how poor the edge correction is. You'd have to be constantly trying to keep the object centered, and by the time the scope settled, you'd have to do it all over again! Of course, if your scope/mount tracks, this isn't an issue. Also, if you have really strong astigmatism in your observing eye, you can see it in views at 1mm and below sometimes, necessitating wearing eyeglasses to get the sharpest image possible. This isn't going to happen with an ortho below 25mm.

Maybe I missed it above, but do you have significant astigmatism (above 1 diopter CYL) in your observing eye? If so, you'll probably want long eye relief in your lower power eyepieces so you can wear your eyeglasses at the eyepiece.

Yes, moving your mirror forward to reach focus with binoviewers will add some spherical aberration to the image. You'll probably never notice it at lower powers, but you might notice it at higher powers. In that case, you might want to swap in a Barlow element to reach focus instead of moving the mirror forward. It has the added benefit of allowing you to use your lower power eyepieces at higher power. That, and it can be difficult to merge high power eyepiece views due to slight collimation issues in the binoviewer not visible with lower power eyepieces.

Hooo Boy! Ain't she purty! 🤠👍

Better hold onto those never released T7 Naglers. They've got to be worth a fortune due to their rarity. 😉

You can try setting it on a water butt stand to raise it up a bit. It's probably a good idea anyway to get it up off the ground to keep crud out of the AZ bearings. You don't want them to get fouled. How about posting a photo it?

Definitely observe some of the brighter, somewhat compact open clusters. Photographs don't do them justice. Also, try some of the large globular clusters like M13. Lastly, view some of the brighter planetary nebula like M57.

Back in the day, there was a line of Zeiss professional monocentrics mentioned in a post on CN. I'll cut and paste the text from CN user vahe here since it bears worth repeating: As promised I contacted my fried who owns these pro Monocentrics with additional questions, here is his reply: “Here is some more information about these remarkable oculars. 1) The focal lengths I reported to you for the Professional Monocentrics are correct, and there were no other focal lengths made. None of these eyepieces were available from either standard or limited production. They were only custom made for observatories to use with various large Zeiss telescopes and astrographs. They differ from the amateur monocentric designs in 5 ways: first, the spec level on the design was much more tightly controlled and the level of polish was reported to me to be about twice as fine as the amateur oculars- the highest level Zeiss Jena was capable of; second, they were designed to work down to f/4 whereas most of the f/l's in the amateur monocentrics were designed to work down to f/6; third, they are highly corrected to provide a flat field over a large area to match the large film plates used in the various Zeiss camera systems; fourth, they incorporate some glass types that were not employed otherwise and were proprietary Zeiss melts; finally, they were much more expensive originally than the amateur monocentrics, which is understandable given the custom nature of their production and the extremely fine level of design and finish. I have never seen one advertised for sale anywhere. 2) Both the 35.7mm and 41.4mm were made in two versions. One is the solitary monocentric, and the other adds a field lens to the assembly so that in these longer focal lengths, the field curvature continues to be controlled over very large areas- for the fastest observatory astrographs Zeiss made. I have both versions, and after 15-20 years of careful comparison prefer the one with the field lens as it is more highly corrected and the field lens completely disappears in use. The field lens appears to be more extensively coated than the monocentric assemblies, whatever the case, I simply can't see it in the light path. 3) I would agree with your European friend that the 18.5mm Professional Monocentric is a special ocular, however I have found it to be second to the 24.6mm. This is after comparisons in both fast and slow 8" triplets, the 10" Maksutov, and three Zambuto reflectors from 12.5" to 20" in aperture, as fast as f/4.3 uncorrected for coma. 4) Over a long period of time, I have compared these eyepieces to sets of the original ZAO's, ZAO II's, amateur Zeiss Monocentrics, and three other brands of monocentrics. The Zeiss Professional Monocentrics are notably superior in every focal length. So much so, that I have sold all of the others except for a few outstanding f/l's that seemed to me to be the standouts in the other Zeiss designs- e.g. 25mm original ZAO; the 10mm and 16mm amatuer Zeiss Monocentrics. I did not keep any of the other brands of "monocentrics". In my opinion, there is a bigger difference in low level contrast, sharpness, and detail in the Professional Monocentrics and the ZAO's than between the ZAO's and other high-end orthos or the most highly touted of the other "monocentrics". 5) When used in combination with high quality barlows or Powermates, the Zeiss Professional Monocentrics remain notably superior to comparable effective focal lengths in any of the other eyepeices I have used, including the ZAO's. This is what surprised me the most, originally, but my experience has continued to confirm it over time. This result provided remarkable flexibility early on, before I acquired the complete sets of focal lengths. It allowed me to design two planetary telescopes around a couple of the eyepiece focal lengths, especially the 24.6mm, then vary a full range of planetary powers with various barlows or Powermates. It is my understanding that only about three dozen of these were ever made. I eventually located and purchased most of them, paying very dearly to complete some of the f/l's. The observatories who had them were in six different countries, and as they switched from film to digital during the 90's and early 2000's I was able to acquire them directly. The most any single observatory had was 2 focal lengths, so its been quite a project and the last one I located was around 2006. There is a number, in the single digits, that seem to have disappeared over time. It sounds like one of your European friends might have a couple of those and is enjoying them very much. I thought it made sense to locate and secure these before they all disappeared as they are both historically significant and in use, pellucid and sublime." Vahe

Update on this thread. Meade is now owned by Orion USA as of June 1st, 2021! Basically, the bankruptcy court awarded Orion substantially all of Meade's assets to settle the lawsuit that led to Meade filing for bankruptcy. My prediction that this would happen was correct! Had Ningbo Sunny simply paid $500,000 or so like Synta/Celestron did to settle out of court with Orion, they would still own the Meade brand. Optronic Technologies, Inc. (dba Orion Telescopes & Binoculars) ("Orion") (est. 1975) today announced the formation of Meade Acquisition Corp. (dba "Meade Instruments"), an affiliate of Orion that has acquired substantially all of the assets of Meade Instruments Corp. ("Meade") (est. 1972), following the approval of the United States Bankruptcy Court for the Central District of California.

I've never heard that. I highly doubt it because microscope eyepieces are generally compact for binoviewer usage. I could believe the NAV-SW being a spin off of either microscope or spotting scope eyepieces, though, since they are so compact. I recall reading on CN (but I can't locate the discussion now) that Al Nagler related a story at a star party of having met some Nikon optical designers at some point at a conference or some such. They freely admitted that they reverse engineered the Ethos eyepieces as the starting point for the NAV-HW line. Since TV never patented the design, and it was merely the inspiration for their design, there were no hard feelings.

A 127mm Mak or Heritage 130p/150p would probably tick most of your requirements boxes. The Mak would excel at higher powers after a 30 minute cool down. The Heritages would excel at lower power views while still being quite capable of higher powers. Don't forget to figure in the cost of a mount for the Mak. The Heritages will need something to set them on. 5" SCTs don't typically provide as good of views of planets as Maks of a similar size. I don't know if your budget would stretch to a 6" SCT or 150 Mak. You might also look into finding a used 8" SCT. Older ones are cheap as chips in some cases because so many have been sold over the past 50 years. A well collimated and well cared for 8" SCT will run rings around most 5" or 6" CATs and reflectors.

A related question would be, would Nikon have come out with the NAV-HW line if the Tele Vue Ethos hadn't already proven a market for them? Would other companies have made well corrected 82 degree UWA eyepieces if the Tele Vue Nagler T1 hadn't already proven a market for them? Maybe they would have eventually, but I'm pretty sure TV lit a fire under their collective behinds to play catch-up. Even military eyepieces of the 1960s to the 1980s with their huge per item price and huge sizes weren't really up to the level set by TV in the 1980s and beyond.

That's usually caused by reflections off of the interior of the rear baffle tube. Try putting flocking material in it. Generally, just roll it up in a tube after cutting it to length and push it up in there without removing the sticky backing covering. Friction will tend to keep it in place.

It seems like fewer Brits than Americans live in homes large enough to have a dedicated workshop, whether it be in a shed, part of a garage, or in a basement. It really helps to have a place to store and use power tools for wood or metal working. Australian homes rival and even best American homes for size on average. I wonder if Australian ATMs are more prevalent than UK (and American) ATMs as a result?

The heavier one probably has a chromed brass barrel that accounts for the extra weight.

I take the back seat out of my Chevy Astro van and put the solid tube Dob vertically in a corner in the back corner. It's packed in with other gear, so it doesn't fall over. I also have a 15" truss Dob that folds up into a 24" square cube with the truss tubes in a slip case. The challenge with it is that it weighs over 100 pounds packed. It takes two people, one on each side handle, to lift it out of the back of the van onto a wheeled platform to move it to the observing location.

IIRC, the 56mm fetches $185 to $225 or more on CN classifieds, the 40mm a bit less, and the 32mm is in the ~$130 range. Given that they all appear to be in mint condition, you might be able to get a 20% or so premium for them. All this assumes a similar level of demand for them in the UK as in the US. Probably $450 to $550 (converted to GBP, of course) for the set would be fair if you don't want to break them up.

Yeah, not a fan of heavy eyepieces in my smaller fracs due to them causing my alt-az mount to turn turtle above 60 degrees altitude or so. To counteract this, I hang about 2 pounds of weight off a bolt sticking out 4 or 5 inches at 90 degrees to the telescope tube from the mount's altitude axis itself. It rises perfectly in opposition to the eyepiece in the diagonal to keep things in balance while doing almost nothing to cause imbalance at lower altitudes.

Actually, I consider 2 blocks the minimum, but 3 works better long term. Over time, the separator blocks can tend to tear away from their neighbors, depending on how tight the fit is and how rubberized the exterior of neighboring eyepieces are.