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The Magnificent Meade 127ED
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The Magnificent Meade 127ED
A fresh look at an old ‘scope
By Neil English
It's true; Heaven forbids some pleasures, but a compromise can usually be found.
As a telescope enthusiast, I’ve seen many instruments come and go over the years. But you certainly learn from some ‘scopes more than others. As most folk will probably now appreciate, I have a fondness for long focal length refractors. They don’t just look cool; they almost always deliver the readies within the remit of their aperture.
My 4” f/15, for example, is the finest telescope I’ve had the pleasure of owning in its aperture class. It has a personality all of its own, a caricature that resonates nicely with my modus operandi. You see, I’ve always been a guy who likes to observe on a whim. Quite often, I have little time to meticulously plan an observing schedule and the instruments I most use – small refractors – allow me to engage with the sky more or less immediately. I have found, through experience, that small, well made achromats, of classical prescription (>f10), are particularly adept at delivering diffraction limited images in all weathers.
But, while a 4” refractor is a versatile instrument, producing interesting images of the planets and the brighter deep sky objects, larger instruments, given proper acclimation, and under good conditions, serve up far more exciting views. And with the winter of 2011-12 promising to show up some killer views of the superior planets –Mars, Jupiter and Saturn - I was in the market for a larger instrument that could allow me to make that observing time especially worthwhile.
But what instrument to choose? Personally, having ‘re-discovered’ the many attributes that make classic achromats perform so sweetly in the field, my first choice would have been a heavily mounted 6” f/15 outfitted with a high specification lens. But that big yin is still in my future when I have the leisure time to attend to it.
A more manageable 7” f/15 Maksutov was also in the running but it’s annoying thermal issues in my harsh winter climate rendered it decidedly ill-equipped to meet my eclectic observing culture. No, it had to be a refractor!
And not any old one either. Six inchers, I’ve found, would be too big to use quickly. A 6” I recently put through its paces took about two hours to acclimate to my shivery spring nights, which for me, was an unacceptably long wait. A 5” doublet would cool much more quickly, making my kind of observing just possible.
I came across an advert for a used Meade 127ED refractor. Not the current triplet, but the older doublet; the units advertised in the major astro-magazines throughout the 1990s. They were drool-worthy alight, stylized as they were astride a nicely designed LXD 600/650 mount. And the user testimonies, in retrospect, were intriguing too.
It turns out that earlier models - produced in 4-, 5, 6 and 7 inch f/9 formats had some quality control issues. Several users reported an annoying tendency for the rearward ED element in the objective to become decentred, necessitating frequent re-adjustment. But I had been assured by the previous owner that no such issues attended this particular telescope. Other folk complained that it wasn’t a true Apo, ‘just a well corrected achromat.’ Now, the latter comment really piqued my attention! The suspense was killing me. So I took a chance on it, and after testing it out for a few nights, I knew I had an instrument that was a keeper. To see why, read on.
First up, it is surprisingly light. The tube plus standard accessories (including rings, mounting plate and 8x50 finder) tips the scales at about 21 pounds. What’s more, being a doublet scope it’s fairly easy to mount symmetrically and far less problematical than a more front-heavy triplet design.
Figure 2. The 5” Meade stores away neatly in a simple wooden box.
The dew shield, I decided, was too short and stubby to be of any practical value, so I removed it. That would also help the large lens acclimate that little bit faster by allowing the air round it to circulate better.
Figure 3. With the short dew shield removed, the lens cell gets better air circulation
The objective is very clean and in good condition, despite being used regularly by its former owner in our damp climate. There were a few deep paintwork scratches on the underside of the tube, but these were cosmetic only and therefore likely to dent an ego more than the views.
Figure 4. A nice lens that’s been around the block a few times.
Only the front surface of the forward element appears to be EMC coated. In this particular design, the ED element FPL-51 (FK01) is rearward, steeply curved and accordingly has very thin edges. Given that these were apparently hand figured, one at a time, in situ, by optical technicians that had never previously worked such soft glass with these steep curves, the company apparently had a difficult time getting the figure on the ED element right and smoothly polished, and didn't want to take any chances altering the figure or roughening the surface with their then-current coating formulations and technology. I now understand that this was the usual procedure at the time, as the Vixen Fluorite series, the Astro-Physics Star12ED (doublet), and Tak FC-100 to name but a few also had uncoated rear ED elements. These telescopes all enjoyed a loyal following in their day and indeed are considered as modern classics.
Figure 5. The strong reflection from the uncoated low dispersion element of the Meade 127ED
My unit arrived with a retro-fitted, dual speed Baader Steeltrack focuser. The owner offered to provide the original focuser too, which was despatched a few weeks later. After using this new focuser for a while, I discovered that it was not hermetically sealed with the main tube. Nor did I like the colour coordination. Thus, irrationally or otherwise, I decided to re-install the latter – for better or worse. Yes, it’s big and clunky with a single speed rack and pinion. Movement is also a bit sticky in cold spells. But all things considered, I still preferred my beat up old focuser, warts and all.
Figure 6. Me no like: The scope came with a retro-fitted Baader Steeltrack dual speed focuser
Figure 7. Out with the new and in with the old: The 127ED re-unites with its original focuser.
The star test on the Meade 127ED was excellent. It shows only very slight under correction when fully acclimated. Colour correction is very impressive; in a different league really to my 4” F/15. But for the record, first magnitude stars like Vega and Capella show a very mild purple halo around them in sharp focus. To my eye, these haloes are very fetching.
The Meade 127ED is a first rate double star instrument that, under average or good conditions, meets or exceeds the efficacy of my binary killer, the 4” Skylight f/15. Propus (Eta Gem), Theta Aurigae, Eta Ori and Mu Cygni were easy with this telescope. It also makes light work of Pi Aquilae, a difficult 6th magnitude pair with a separation of 1.4 arc seconds. Where the split is marginal in the 4” f/15, the Meade renders much more convincingly.
There are some other differences though, between this f/9 scope and my classic f/15. The latter really is the ultimate grab ‘n’ go scope in the sense that you can take it out from a warm room to the chill of a winter evening and it will serve up diffraction limited images at high power within minutes. I attribute this to a number of factors, most notably, a smaller objective with thinner lenses that have coefficients of thermal expansion between 50 and 100 percent less than any low dispersion glass used in contemporary refractors. That means it undergoes significantly less distortion during cool down. The larger Meade most certainly takes significantly longer to acclimate (see below). Indeed, even after thorough acclimation, there was always a difference, to my eye, between the images thrown up by the long focus achromat and Meade 127ED. The long ‘scope almost invariably delivered calmer images with slightly greater contrast than the Meade.
Finally, I have gotten so used to using f/11 - f/15 optics of late that returning to f/7 is a near impossibility for me. I am shamelessly addicted to effortless precision focussing, first time, every time. When the Meade came along, f/9 was (and still is) a bit of a struggle, but it's a compromise between the old and the new.
Figure 8. A somewhat unfair but enlightening comparison.
For an idea of how long it REALLY takes a refractor of these specifications to FULLY cool off, take a look at the graph below, compiled by Mardina Clark of Tacoma, Washington., USA. You can see from Mardina’s plot that it takes 50 minutes for the objective of a 5” f/9 doublet to match its tube temperature.
Figure 9. Graph showing cooling curves for a 5” F/9 doublet refractor. See: http://www.cityastronomy.com/cooldown.htm (used with permission).
Contrast that to the findings of Allister St. Claire, who reviewed an air spaced 5.2” f/12 triplet Apo over a decade ago, reporting that it took at least 90 minutes to fully acclimate under his conditions:
“The APO MAX takes 1.5 hours to cool down to a temperature where it can sustain 300x on the planets. This is coming from an unheated garage to the outside. It's interesting to observe the cool down process as every 15 minutes or so I can increase the magnification by another 30-50x and maintain a solid image. It's sorta like I'm sneaking up on the planet if I observe while waiting for it to cool. The star test will completely smooth out in 2 hours but I find I can't detect any degradation in the image for that last 30 minutes. Perhaps if I were a more skilled planetary observer I would see it but as of today, I can't.”
Allister used a really neat way to monitor the progress of acclimation by measuring the time it took for the intra and extra focal diffraction patterns to ‘smooth out’. I adopted a similar strategy with the 127ED and found that complete acclimation (with a temperature delta of 20 degrees C) took about 50 minutes, in agreement with Mardina’s graph. That said, the images were quite useable in half that time, so long as I didn’t push the magnification too high.
Similar findings have been reported in comparisons between larger doublet and triplet refractors. Check out Dave Novoselsky’s 2003 review here;
Under the stars…
Selene at first quarter is just beguiling in the Meade 127ED. Craters and mountain ranges were resolved cleanly and with no false colour that I could make out. With a 40mm wide angle eyepiece, I detected a greenish rim to the full Moon which is probably related more to lateral colour caused by the eyepiece than longitudinal error caused by the telescope’s objective. At 190x, I watched in amazement as the peaks of mountains that girdle the crater rims near the lunar south pole became lit up by sunlight surrounded by a sea of blackness and set well beyond the day/night terminator. I saw a ‘double peak’ that looked for all the world like a close binary system. It was like something out of the Twilight Zone!
Saturn is a target that quickly smashes the dreams and aspirations of those who believe the current run of short and medium focus achromats can compete with a similar sized apochromat, or ED scope for that matter. A recent pretender, embodied in a 6” f/10 achromatic prescription, was comfortably put to bed by the 5” f/9 Meade 127ED in critical, high power tests. Don’t get me wrong; the 6” scope trashed the 5 incher on EVERYTHING else – which is something to seriously contemplate. But the excessive colour on the lens just took the shine off of the image of the ringed planet at 300x, where the smaller scope, endowed with a single, inexpensive low dispersion element, stubbornly refused to countenance defeat.
I have enjoyed many memorable views of Jupiter of late, but I will only describe one particularly vivid encounter. It was the end of August 2011, but there was nothing august about the conditions that evening, or all night for that matter. Transparency was excellent but it was quite breezy throughout the observing period.
I first inserted the 5mm ortho yielding 229x for a lark to see how bad things were going to be. Well I was very impressed! At this super-optimal magnification, the planet was razor sharp and I could still see a wealth of atmospheric detail. I backed down to 190x using the 6mm ortho and the image improved still more; the atmospheric features this instrument was showing was eye wateringly good. There was a constant breeze in the air throughout the observations, yet the clarity in the oblate Jovian disk was superb. I could make out at least a half dozen bands (possibly as many as 8). A wealth of structure was seen in the North Equatorial Belt (NEB) and dusky marks in the planet’s south polar region.
I detected the merest trace of colour on the planet’s limb but to mention it almost seems silly. At the highest powers tested (570x), the Medicean ‘stars’ were presented as tiny disks and were quite un-stellar like. Indeed, this scope made light work of differentiating them on the basis of their colour, albedo and slightly different angular diameters.
I have looked through quite a few 5 inch refractors before; some excellent and some mediocre, but all on a casual basis i.e. for a few minutes at a time and often under less than optimal conditions. But all I can say is that I couldn’t see how the views of Jove I enjoyed in the 127ED could be meaningfully improved. It was quite simply stunning! The image was most certainly in a different league to any 4 inch scope I’ve turned on the planet.
A more revealing test came when I compared and contrasted the views through the Meade 127ED with a 6” triplet Apo on an unseasonably mild autumn night (with little difference between inside and outside temperatures). Although the latter performed beautifully, displaying sharp images with no colour, either in or out of focus, it took considerably longer (at least twice as long in fact) for the images to stabilise compared to the simpler Meade doublet. Indeed, apart from the fact that the 6” triplet served up a brighter image with slightly greater contrast than the Meade, the images were otherwise very comparable in terms of the Jovian atmospheric details I could discern. I was left wondering how often I’d see a larger refractor like this, with lots of glass up-front, outperform the less complex 5 incher.
Figure 10. Is a 6” triplet Apo overkill for the backyard visual observer?
Meet the eyepiece leveller…
One of the great unsung virtues of a longish doublet like this is the fine performance of low cost 2” eyepieces for wide field observing. Case in point: my dusty old Antares 40mm Erfle. It has a lot going for it; 20mm eye relief, comfortable 65 degree AFOV, a huge eye lens and relatively light weight. But stick it in an f/6 ‘scope and the limitations of its design quickly come to the fore;- not bad over 70% of the field but noticeably distorted further out. Now, let the same eyepiece intercept the shallower light cone of an f/9 refractor and you have a real winner on your hands. Panoptic performance for peanuts!
Figure 11. New lease of life: Inexpensive 2” eyepieces perform handsomely in the Meade 127ED.
That same eyepiece, serving up a decent 29x in a 2.2 degree true field, beautifully frames the vast majority of deep sky objects. The star clusters of Cassiopeia – NGC 457 and NGC 7789 particularly - open up in this ‘scope like flowers in a summer meadow, and in ways that easily transcend anything you’d see in a 4 incher. I am mildly excited about trying out some other economical 2” eyepieces with this telescope, especially minimalist designs such as a big 56mm Plossl, a Konig or Moonfish, or even a modified orthoscopic like a Paragon or Aero.
Back to the future: when compromise is worthwhile…
At this stage, I wanted to call your attention to the original blurb Meade Corp used to launch these instruments:
“In early 1991 Meade engineers and opticians set out to develop the most advanced, mid-aperture apochromatic refractors ever made available to the amateur or professional astronomer. In studying all of the glass-types and designs available, it rapidly became clear to Meade optical designers that an air-spaced ED-glass doublet objective lens met all of the required design criteria: apochromatic performance with absolutely superb color corrections at all photo-visual wavelengths, even at the highest magnifications; relatively light weight for rapid thermal equalization; and excellent durability and resistance to weathering.
The objectives included with Meade ED apochromatic refractors are manufactured entirely at the Meade Irvine facility and utilize the highest-grade optical glasses available; they are free of striae and other imperfections that can degrade optical performance. Each lens is individually manufactured, pitch-polished, and hand-figured by a master optician to reach the highest levels of resolution, contrast, and correction obtainable. “
In the above quote, I’ve deliberately highlighted a few things that I found of interest in assessing the performance of this telescope. Did this scope live up to the company’s original claims? Broadly, yes! OK, it has very low levels of in focus colour on bright subjects, but I’ve learned not to conflate colour correction with absolute optical quality. The telescope did acclimate quickly, even under large temperature gradients, it is lightweight and relatively easy to mount. The fact that the clean lens on the Meade 127ED it is still serving up razor sharp images after all these years is testimony enough to its ‘excellent durability and resistance to weathering.’
Maybe I’m lucky, or maybe I just have good taste in telescopes. Whatever it is, I am really glad I encountered this instrument. And I’ve seen them go for under $1000 on AstroMart. But it’s not just me who finds these instruments delightful. Experienced telescope reviewer, Ed Ting, also had good things to say about these refractors:
“I am often asked by readers if they should purchase these Meade ED refractors. You may be surprised to learn, my answer is usually "yes" -- provided they do so from a reputable dealer. At their best, these Meade APOs are capable of near world-class performance, and they cost a lot less than the "luxury" brands. However, as we have seen, the quality can vary quite a bit from sample to sample.”
I also found some older reports that suggest the Meade 127ED delivers images broadly equivalent to much more expensive – and revered – medium focal length doublets such as the venerable Takahashi FS 128. Indeed, that was also the opinion garnered by Sky & Telescope columnist, Jay Reynolds Freeman, who, several years back, did a shoot out between this ‘scope and a Takahashi FS 128 and Astro-Physics 130 EDT f/8, with some of his observing mates. Indeed, if I recall correctly, he attributed the differences between these instruments to be about as important as the difference between an excellent and mediocre eyepiece.
I decided to take the guesswork out of the likely optical quality of the Meade 127ED by contacting Vladimir Sacek, optical theorist and creator of the fantastic online optics resource www.Telescopeoptics.net. Vladimir kindly provided an OSLO analysis of the instrument, based on a few reasonable assumptions about the curvature of the elements.
Figure 12. OSLO ray trace analysis of the Meade 127ED. Data courtesy Vladimir Sacek.
As you can see, the Meade 127ED does very well indeed! Intriguingly, if one were to accept a leading technical definition of Apo – with at least ¼ wave p-v over the C to F visual range and at least ½ wave p-v and ½ wave or less for g and r Fraunhofer lines, the Meade doesn’t quite make it. That said, its polychromatic Strehl exceeds 0.93, which puts it real close to the generally accepted "sensibly perfect" 0.95 or better (not that anyone could see the difference between 0.93 and 0.95 system). For all practical purposes, the 127 can be regarded as a true visual Apo, and a photographic semi-Apo.
A better way forward?
My experiences with this 5” refractor has taught me a great deal about how a telescope ought to be designed in order to meet the demands of my fickle climate, where large temperature swings are common (I store all my scopes indoors), especially in winter, and often during times my skies present the best observing real estate.
At f/9 and with some low grade exotic glass, the Meade 127ED puts up beautiful images. The spherical correction is almost perfect in mine and the contrast is more than acceptable. It just ticks all the boxes. For a modest investment, and just a little more planning, it takes your backyard observing experience to a whole new level of enjoyment.
The discontinuation of the Meade telescopes, together with other 5” and 6” doublet apochromats, such as the delightful Takahashi FS 128 and FS 152, was a grave mistake in my opinion. These scopes, with their decent f ratios (f/8) and simple (doublet) design made them hard to beat in the field.
In experiencing at some length the modestly priced Meade 127ED, I think the serious amateur looking for a larger refractor can get a better deal. What’s more, these putative ‘visual Apos’ don’t necessarily require optical prescriptions that deliver perfect *in focus* colour correction either. A number of cost-effective glass combinations that deliver most of the ‘f/15 performance’ may well be commercially viable.
For example, a well executed 6”f/9-10 KF3/FPL-51 doublet would be a cracking telescope. It would have a high polychromatic Strehl that can be attained and maintained in the field frequently enough to make such an investment worthwhile. That same instrument would cool off considerably more quickly than the current suite of air spaced triplets on the market. I mean, a 6” triplet objective is massive to start with. What’s more, the fluorocrown element’s very high coefficient of thermal expansion, insulated between two other lenses in the cell, doesn’t exactly help matters when it comes to enabling backyard observers engage quickly with their subject targets. And that’s the crux of the matter for me - do you want a high performance refractor that promises the Universe on paper or one that gets you there without hyperbole? Alas, a posse ad esse non valet consequentia.
Figure 13. Ahead of its time: the all American Meade 127ED.
I’d like to thank Jim Barnett (Petaluma, California), Jeff Morgan (Prescott, Arizona) and Vladimir Sacek (www.Telescopeoptics.net) for interesting discussions about this instrument.
Read more about Hi-Tech spy glasses in my book Choosing and Using a Refracting Telescope (Springer).
My sister book, Choosing and Using a Classic Scope will be published next year by Springer.
- bgi, Arief M., Stew44 and 1 other like this