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Brandon Eyepieces

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This story begins with a tragedy, but since it ends happily, it is what the Greeks called a comedy. It began with the purchase of a set of five Brandon eyepieces and Dakin Barlow from a source outside of the U.S. (In case someone I know is reading this, this set is for another residence.) Upon arrival, two problems presented. Since the seller had mentioned he used these with his Questar, I had assumed the eyepieces were the special, Questar, threaded barrel version. They were, instead, the standard 1.25” slip fit version, which, while workable, is not optimal. And an examination via transmitted light from a high intensity LED flashlight showed a lot of dust. They needed cleaning, but was the service worth the money, considering they were the wrong eyepieces?

I considered selling them, and made one offer, but I’m glad it didn’t go through. A second examination, shining the flashlight on a field lens showed some pinpoint damage to the coating. One of these had a “bulls eye” pattern. From prior experience with old optics, I suspect this pattern as an indicator of a very early fungus infection, though I am no expert on this matter. It wasn’t even through the coating, but prophylaxis was in order. At this point, I felt really stuck. I could take them apart myself, but I lacked the custom spanners to do the job efficiently, and I know only some of the tricks of cleaning optics. Handling small lenses without recontamination them is one trick I don’t know.

Steeling myself for the worst, I waited for the weekend to end so I could contact the maker of the eyepieces, Vernonscope. To understand why I was apprehensive, let us consider the standard of care with a typical U.S. company now days. You call them up and they tell you

  1. If it’s in warranty, we will repair/replace at out option.

  2. If it’s out of warranty, tough.

  3. You want to buy parts? Tough.

  4. You would like to speak to my supervisor? He’s busy.

  5. You’ve received three defective units in a row? Sir, all our products are carefully inspected by Tweedledum and Tweedledee.

All this is told to you like you’re having a problem with your cell phone, and the problem is YOU. It’s the art of the blow-off, perfected in spades. When I called Vernonscope, I hoped for something a little better. Sometimes a small company will do small favors, like stick something in an envelope they don’t have a price for, or work on a time-and-materials basis. I picked up the phone and dialed. No answer. Uh-oh, I thought. They have a lousy internal phone system. I tried a while later. The phone picks up; there’s a voice; it’s the guy who makes the eyepieces. The reason he didn’t pick up before is that he was busy making them.

I tell him a little about my problem, and the conversation veers off to the weather in Candor, NY, which is upstate, talking stocks with his optometrist friend, and his ranked status as a sprinter in the Senior Olympics. Strangely, he seems to have no desire to get me off the phone. I am waiting for the shoe to drop, “they’re toast, buy new”, but it doesn’t happen. At some point, I tell him my sad story, and something remarkable happens.

He cares. He earnestly cares that people should enjoy using his eyepieces, and really wants to help if something gets in the way. He sells a pretty fair number of eyepieces a year, and if somebody with an old set like mine has a problem, well, he wants to take care of that person. And he doesn’t have a bean counter on his back to get in the way of his personal gesture.

He told me to put them in a USPS Priority Mail “shoebox”, which fits the presentation case, and he said that when they arrive, “he gets right on it.” Can you believe this? I was expecting, “as time permits with our available production schedule”, but Don Yeier (that’s his name), drops what he’s doing to work on somebody’s crummy eyepieces. Happily for him, his son works with him.

But they were in the wrong barrels for a Questar. He said he had some “seconds” barrels, and he could swap them. He would examine each eyepiece in the set, to determine whether the optics were worth it. He would clean them with acetone, and I would have them back by Saturday (they left on Monday.)

I will not tell you what he charged for this, but I would say that in my lifetime, this has to have been one of the two greatest acts of kindness, by a business to a customer, that I have ever experienced. The other was by Questar, but that’s another story. Taken together, it says something about the relationship between the very small companies that make the finest telescopes and optics, and the people who use them. I’m afraid I have to leave the big companies out of this.

The eyepieces arrived on Saturday. I had been sure the mark on the Barlow was a permanent mark, because it did not succumb to vigorous rubbing with acetone. (Don, you didn’t swap that element and not tell me, did you?) The worrisome coating marks were now faint imperfections. The barrels had been swapped. I think that in doing so, Don made a personal judgement about me; namely, that I would never use the improved cosmetics to misrepresent the rescued eyepieces to someone else. I pledge never to do so.

But what is a Brandon eyepiece, and why do many consider it special? It is frequently stated that it is a kind of Plossl, but it is not. While the outer surface of a Plossl field lens is concave, that of a Brandon is flat, while the eye lens is slightly convex. Very clear pictures of the differences are at http://www.quadibloc.com/science/opt04.htm According to Chris Lord, author of “Evolution of the Astronomical Eyepiece”, the Brandon most closely resembles the “Zeiss duplet”, but turned around backwards. So what makes the Brandon special?

Chester Brandon was one of the designers of the Norden bombsight. In his work for the U.S. government, he had access to the most exotic glasses. He could have even used a radioactive thorium glass for Uncle Sam, but we are fortunate that, for the eyepieces that bear his name, he did not. He chose lanthanum, a member of the “rare earth” family, high in the periodic table. The apparent simplicity of the four-element design hides the fact that it uses more different types of glass than many complex designs, a different glass for each element. There are two extremely high index glasses in the design, both outside elements: barium flint, and a “double extra dense flint”. The interior elements are a lanthanum crown, and a light crown.

In recent designs, lanthanum has been the golden ticket to high eye relief or extreme fields of view. But these features come at a price. By using only four elements in two air-spaced groups, Chester Brandon chose not to pay the price. For reference, the currently most expensive eyepieces in the world, the virtually unobtainable Zeiss Abbe Orthoscopics, have four elements in two groups. All the newer, vastly more complex designs play second fiddle to these. But why?

Different strokes for different folks. Many desire an immersive view, the “spacewalk” experience. Others favor critical viewing; planetary, searching for the faint whiff of a spiral arm, or the faintest star. If you’re in the first category, buy a modern, complex design. But if you’re a critical viewer, the fewest glass elements, made of the finest glasses, are arguably better. This is why some diehard planetary observers swear by ‘solid” eyepieces, those completely cemented together. But such eyepieces have very limited field of view and eye relief.

Perhaps Chester Brandon took inspiration from the Zeiss when he chose no more than two air-spaced groups. Abbe achieved 40-45 degrees of view, but with exotic glasses, Brandon achieved 50 degrees, and eye relief equal to 0.8X the focal length of the eyepiece, which is an excellent number down to 16mm. Like the Abbe, the Brandon is an orthoscop. This means that the magnification is constant from center to edge; no pin cushion distortion. The Brandon design also has extremely high contrast, and no ghosts.

Poor skies and cold temperatures prevent me from offering even an informal astro perspective. But I have tried terrestrial viewing. In a Questar 3.5, there was an obvious difference between the Brandons and a B&L Plossl. The Plossl was slightly soft, while the Brandon 32 and 24mm exhibited the crystalline sharpness that many consider part of the Questar legend.

But it is really superfluous for me to say anything, as Chris Lord has done a double blind test, which you can read here: http://www.brayebrookobservatory.org/BrayObsWebSite/HOMEPAGE/PageMill_Resources/Comparison%20test%20of%20TVPlossl%20vs%20Brandon.pdf . Chris answers the important question: What scope are the Brandons good for?

All eyepieces have a critical focal ratio. If the scope is faster than the critical number, the eyepiece fails to perform. The critical F ratio for both Abbes and Brandons is F7. This includes all Maksutov and SCT type instruments, but not fast refractors or reflectors. This point cannot be overestimated. If you pair a Brandon (or Abbe) with a long focal length instrument, the result is everything the scope is capable of. If your scope is fast, look for one of the new designs that actually contain an integral Barlow. Unfortunately, there are no classical orthoscopics that work well with fast scopes, but some designs approach these in performance. At F6.9, Chris Lord said, “Definition was noticeably superior in the Brandon…” But this was not the case with a Newtonian at F4.7. Whether this is because F4.7 is too fast, or because some eyepieces “accidentally” compensate for the coma of a fast reflector, I do not know.

In passing, I remark about the Questar legend. In recent years, this has been pooh-poohed, as in “There are no magic telescopes.” While there is no magic, let us examine whether there is any reason why a Questar could outperform a “perfect apo.” It is commonly believed in amateur circles that the central obstruction of the Questar means that an apo will best it. Would you believe me if I tell you that exactly the opposite is the case? The knowledge comes from the author of the website, www.telescope-optics.net, where it is stated, “Obstructed aperture has significantly better contrast transfer - even from that of a perfect aperture - in the right half of MTF frequency range (i.e. for details smaller than 2ëF linear, or 2ë/D in radians. Even in the left half of the graph (range of resolvable low contrast details), obstructed aperture has an edge.”

Amateurs seem to believe that the size of the second Airy ring is the determining factor. What they do not understand is that, for a range of obstruction sizes, the disk itself is actually smaller and brighter! A Questar actually has a higher MTF (modulation transfer function) at all frequencies, compared to an unobstructed instrument. I urge disbelievers to read the section “obstruction”, in the above named website, see the graph, and look at the red line. It is “above” the line for unobstructed aperture. And this means, that to a small degree, a well-manufactured Questar will outperform an apo in the resolution of fine details. MTFs do not lie.

To keep this edge is one of the two reasons Questar chose Brandons.

Amateurs seem perplexed that Brandons are not multicoated. Thomas M. Back, founder of TMB, while discussing his own monocentric designs, remarked that Brandons do very well with single layer coating because the glass is very dense. But there is also the matter of narrow angle scatter. The claim is made that, while multicoatings reduce total reflectivity, they put more of the reflected energy very close to the direct ray itself, causing loss of sharpness. Some scoff, saying it is a ploy to save money.

I wondered about this myself, but an answer came in an unexpected way. I have on order a Questar Astro 7 with a quartz mirror. According to both Questar and Company 7, quartz mirrors are easier to finish to a higher tolerance than either Pyrex or Zerodur. “Quartz cuts like butter.” I wanted my Astro 7 to have broadband coatings, but Questar does not offer a quartz mirror with broadband, stating that the broadband option would mask the superior quartz mirror. Does the Brandon choice to use a single MgFl layer have any penalty at all? Maybe not. Chris Lord also notes that the Brandons had no internal reflections, and no field scatter.

Since there are classic telescopes, there is a place for the Brandon style. The barrels are simple black anodized aluminum, carefully finished. Some runs are so carefully polished before anodizing that they give the appearance of glossy lacquer. Others have an angular brush. They remind me of bygone days, when a professional astronomer, at the drawtube of a massive refractor, relied upon his eyes for truth. Most of the cost is in the lenses. While there have been “volcano tops”, the standard version has a roll-down rubber eyecup. Even though I wear eyeglasses, I prefer this. I have noticed that, when using interference filters, the slightest bit of ambient light causes me to see the reflection of my own eyes. Only by sealing the eye against the eyecup can this be avoided.

Suppose you want to try a single Brandon. The 24mm has been suggested by some as the best first choice. These eyepieces have no kidney bean effect, because the exit pupil is flat, which is why they are regarded as an excellent choice for eyepiece projection photography. But the 32mm, my particular favorite, has so much eye relief one has to take a little care.

Inevitably, we come to the question of value. Chris Lord, whose double blind methodology should be used more often, points out that a Brandon is not 10X better than a GSO Plossl. This is the law of diminishing returns. But by the same token, at the aperture of F7 or greater, the Brandon approaches the theoretical limit of what can be done. Yet some still spend thousands for the Zeiss Abbes. Bumping the theoretical limit implies that both eyepieces must be very close in performance. As far as I know, there has never been a double blind comparison between Brandon and Zeiss, leaving prejudice as the only guide.

So the Brandon could be a real bargain: Zeiss perfection at a third the price. But there is another reason, which I would have hesitated to mention in prior times. As most of us are aware, there has been a decimation of American manufacturing. America has become a hollow country. The unemployed understand this; others may not. It became a dirty word to say, “Buy American”, but why? Part of this was due to the choices American manufacturers provided us consumers. We bought imports because they were better. We chastised our own, and now they are on unemployment. We abandon our brothers, and abandon ourselves. But in astronomy, this was never true. American telescope makers have always ranked highly in the world. Even the fallen giant, who I will not name, has spawned alumni who, in their small shops, build the most inspired, precise designs imaginable.

John F. Kennedy said, “Ask not what your country can do for you. Ask what you can do for your country.” We should take this to our hearts now. It is more important than a good view of Mars. Yes, we will pay more for that excellent American quality: Questar, Brandon, Astro-Physics, Optical Guidance Systems, RC, Starizona Hyperion, Particle Wave, Mountain Instruments, Losmandy, et al.

If we follow through, there will always be a Don Yeier at the other end of the phone. This is the strength of a great nation.

  • Brian Palmer, george tatsis, caheaton and 8 others like this


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