14 replies to this topic

[asaint]

Reviews

NEW LINK Review of the TMB Mono Review(s)

[Starman1]

The lesson to be learned here is that if you buy TMB SuperMonocentric eyepieces, you want to have them personally tested by Thomas Back, because if you get eyepieces just taken off the shelf, they may be of lesser quality.
What it also says is that until every eyepiece is individually tested, caveat emptor (let the buyer beware).

[norscot]

There is absolutely no point in going through the motions of conducting an "independent" test of equipment that has been specially prepared with that end in mind. For the paying customer, whether the fault lies in poor design or a defective manufacturing process is quite academic - when I hand over hard-earned cash for a premium item I expect the thing to work as well as it's supposed to. Similarly, when I read a test report in an authoritative magazine I expect the test to relate to the item as I can buy it, warts and all, and not to some specially tweaked super-version. That's hardly the case when the manufacturer has been warned in advance that the items in question are about to tested and the results subjected to very public and informed scrutiny. TMB should be congratulated for their professional honesty and integrity in supplying a random rather than a doctored sample for testing, and one assumes that steps will already have been taken to address the apparent and unfortunate lack of adherence to their normal quality control standards in this instance. That is precisely the benefit - both for future customers and for the supplier - of random testing, and the idea of repeating the test just to prove that the next batch of eyepieces has been properly vetted (and I would imagine that this time it will be) before leaving the factory seems a little futile. Arranged tests can be expected to lead to predictable results, and they're generally not worth the effort involved in reading them.

[Starman1]

I should have added:
And it points out the perils of being an early adopter. I, too, have no doubts that quality checks will be more stringent on future batches.

[J_D_Metzger]

Albert certainly makes a lot inferences and draws a lot of conclusions about Gary's review. I wonder, did Albert ever take the trouble to actually talk to Gary about his review and confirm any of those inferences? Just seems like that would have been the appropriate thing to do....

Clear skies,
J.D.

[Daniel Mounsey]

Norscot nailed it right on the nose. I have great respect for Tom Back, in fact I asked to use his star testing method in my planetary telescope article which we plan to release soon. I found Gary's Sky&Tel article fine, however I was amazed that he didn't realize why he was seeing a lighted peak on the Moon that was not as visible in the other eyepieces. Had Gary addressed the fact that the Monos have noticibly more light through-put, he would have realised why this was. As far as I'm concerned, Gary called it like he saw it and I feel that because the other eyepieces were nearly just as good, some are not happy with that. Hey, the Monos are not for everyone and many opinions of their superiority are bias in my opinion. John Pons and I spent three hours going back and fourth between the classic Brandons, Clave's, Monos and .965 Pentax. Both Pons and I agreed that the TMB's were so pure, that they almost gave Jupiter a washed look as if an artist had taken paint thinner and washed up the contrast of the belts. Pons and I actually liked the Brandon's and the Pentax's and the Monos came in 3rd. These tests were conducted with a 10" F-16 Zeiss refractor and a color corrector designed by Roland Christen. We also conducted the same test using an 8" F-9 TMB refractor. Using an 11mm Televue plossl and a 10mm Mono, we were amazed to see that the TMB produced a noticably brighter image than the Televue, even at higher magnification. This is what confirmed its brightness to us. I'm sorry, but when you are spending $250 on an eyepiece, there's no excuse for a lack quality control. That's a lame reason as far as I'm concerned. I also love the RKE, but the 8mm is my least favorite of the design. Even in my planetary eyepiece article, I found the cheap RKE's to be fantastic and one of the top picks, especially for the money. You guys gotta remember that it's getting to the point where were just splitting hairs.
Daniel Mounsey

[Starman1]

Don,

Regarding caveat emptor, the emptor need not be completely driven by his or her caveats. If a manufacturing problem is identified in a TMB Super Mono at any time (even when purchased used, as I understand it), it will be replaced by TMB/APM.

Al Bellg

An interesting side note: I have had occasion (though not often) to actually use 3 of the same eyepiece at the same time in the same scope. One time, I compared 3-22mm Panoptics. Another time 3-8.8mm Meade Ultra Wide Angles. It's a long story as to why/how I got to do this.
Several other times, I have had occasion to compare my eyepiece with an identical eyepiece borrowed from a friend.
My conclusion: there are subtle differences between eyepieces of identical focal length/model/brand!. Of course, I kept the sharpest ones, but I was literally flabbergasted to see differences among identical units.
The differences were very subtle, and identified by sharpness of star images on center, at the edge, and (believe it or not) on the edges of deepsky objects.
These subtle differences were probably related to the quality of polish, optical alignment, and coatings between the eyepieces. At no time did I feel the worst of the bunch was a bad eyepiece, but I did feel that the best of the bunch was noticeably better than the other two in each instance.
Other comparisons I've made have been less conclusive (i.e. I wasn't certain which was better because of viewing conditions).
What does this mean? It means to me that there is a slight production variation in all eyepieces (because they are individually made and because there are so many steps in their constructions that will make slight differences in the final products), and that some of the very subtle differences noticed could be due to those differences.
Of course reviewer A's use of an f/5 scope, and reviewer B's use of an f/8 scope will have profound impact on their findings. It is when the same eyepieces are compared in the same scope on the same night on the same objects that the true differences can emerge.
Does that mean I'm going to always buy 3 of every eyepiece and return the two lesser ones? No. But it does mean that 2 units of anything produced by Man cannot be absolutely identical due to the normal variations in production.
I used to review high-end amplifiers, and, after listening critically, send them to a test lab to get all the figures. Occasionally, a mfr would take issue with a review and send us a second sample. Surprise! The second sample, though it had all the same components as the first, did not measure the same. The inevitable long chain of components, each with a slight variation from perfect, never added up to the same end result--on any two units.
Now, most people, under most circumstances, would never have heard the difference. Likewise, most people, under most circumstances, would never see the differences between identical eyepieces from the same company.
But when you add up polish, figuring, glass, coating, and assembly variations (especially with more air-glass interface surfaces), it's obvious there will be production variations.
And the good manufacturers will take steps to weed out the ones that vary outside the performance parameters (TeleVue does this, for example) so we don't get a bad one.
Nonetheless, there are subtle, slight, differences.
And I suspect these reviewers may have run into them.

[David Rivas]

I have just received the accessories I purchased from Astronomics(they got home two weeks ago). Among them I bought a TMB Super Mono 10 mm for my Celestar 8" .
At first glance, it looks great. I can see a lot of contrast improvement when I watch the moon at 200x(I got UO Orthos. HD 9, 12, 18 and I can detect more low-contrast detail as well as better light throughput through the Super Mono eyepiece.
However, I noticed a very faint yellowish ring along the edge of the field of view...I tried to see if the edge of field performance was afected by this slight yellowish ring but it wasn't so. Anyway I, as a recent member of the Yahoo's TMB group, posted a message in which I asked whether or not this "issue" was normal or I had to send it back to change it. There,I was told that if such a ring was as faint as I mentioned, it was normal. I was also told that defective Super Monos had a strong yellow ring and so not good off-axis performance (for 10 mm and less)
To conclude, Although I have still not watched any giant gas planet but Uranus, all I can say is that I am very happy with my Super Mono 10 mm. performance (in spite of its small fov. I can see the difference...)
As you can tell, I was rewarded with a randomly chosen (Astronomics)great eyepiece...

Regards,

David

[Mike Hosea]

In Gary's review of the Super Monos, he clearly saw something in the edge of field performance that I didn't. It was severe, and it resulted in him giving off-axis performance a two-star rating, "performance compromised during normal use." Thomas Back subsequently identified what Gary saw as an atypical flaw in the eyepieces he tested that would not represent what the typical purchaser would see.

First let me say that I appreciate the level of thought and analysis that you have put into all this.

One thing I do not understand, though, is why the issue of field curvature is so often neglected in discussing edge-of-field performance. Here is a property that introduces dramatic differences in edge-of-field sharpness based on particular pairings of telescopes and eyepieces, accommodation abilities of eyeballs, and focusing habits. Perhaps I see more of this because I insist on focusing the center of field at infinity, with the eyeball relaxed, rather than allowing the center to be moved inside focus to find an "average" focus position.

Anyway, my testing of TMB SuperMonos in two 10" f/5 Newt showed a significant amount of field curvature (I would say "severe" compared to that seen in an Abbe ortho in the same scope), and in approximately the same amount in the 5mm TMB SuperMono that I got from Markus as in an entire set of reference samples tested by Thomas. I do not believe for a second that this was a defect, as correspondingly, I noted in examining both sides of focus that the edge of field showed astonishingly good control of astigmatism at f/5. If it was a defect, then it was a miracle that astigmatism was accidentally controlled so well, as these two edge-of-field aberrations tend to be complementary in simple eyepiece designs. However, even in an 7" f/6.7 Newt the curvature was much less noticeable (despite the OTA having nearly the same inherent curvature as the 10" f/5), so it is small wonder that not everyone gets the same edge-of-field results, even when the samples are not defective. Furthermore, because different telescope designs have different curvatures themselves, one should not even expect the same results in, say, an f/5 apo as in an f/5 Newt. I don't pretend to know which end is up here, but it seems to me that whenever an eyepiece designer decides to leave in a certain amount of field curvature in order to avoid introducing astigmatism in faster scopes, we SHOULD see some differences of opinion on edge-of-field performance.

Personally, I tend to shrug at the edge-of-field properties of these eyepieces. Anybody who is willing to suffer a 30 degree field is probably going to have a drive and keep the object under scrutiny nailed at, or very near, the center of the view.

[spaceydee]

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