S@N's FLT132 review???

[FLO]

I thought the lens cell in the FLT was made by TMB? Does anyone know whether or not this is still true?

The original was designed by TMB and used FPL-51 glass but WO wanted to upgrade the glass to FPL-53 so today's FLT-132 uses their own in-house optic.

[mike bacanin]

It seems the 132 sometimes doesn't have a good time of it when its being reviewed.

I recall Nik Szymanek noting the 132 he reviewed in AN a while back suffered from pinched optics giving the classic triangle-like defocussed star test.

could this indicate some QC issue?

I googled the diffraction spike issue and came across a comment that the spacers intruding too far in would be a cause.

I can't help thinking that one of the reasons refractors are so popular, as an unobstructed design, is the lack of spiders and normally no diffraction spikes.

Mike

[GazOC]

Mike,

I think that was a early problem cause by the lens cell that was fixed in subsequent production runs when WO re-designed said cell.

Gaz

[ollypenrice]

Not just TMB either.

Also, not wishing to spoil anyones fun but do keep in mind that the FLT-132 is one-half the price of the Tak-130 and one-third that of the TMB-152.

...and twice the price of the Meade 127, which has never produced artifacts in my images. My real point is about the review. I just can't believe that in one sentence, with nothing followed up, all the value of the article vanishes. We are back to square one, not knowing whether the scope is worth having or not. I wouldn't want to blame Pete Lawrence. I very much doubt that it was his decision to spend lord knows how long telling us yet again what an apo is and then letting these spikes hang unresolved.

I'm not suggesting the scope is a dog, just that we don't KNOW if it's a dog or not.

Olly.

[FLO]

...and twice the price of the Meade 127

And so it should be, the FLT is considerably better, optically and mechanically.

[ngc2403]

any pictures of the spikes on the stars?

i would be interested to see them. thanks for posting the wee metal spacers pics, i would not have though they would have caused problems.

ally

[KaStern_Former_Member]

Hello Gaz,

I think that was a early problem cause by the lens cell that was fixed in subsequent production runs when WO re-designed said cell.

I am not sure about that. A german Vendor announced some weeks ago that he was

going to send the 132mm f/7 triplett Apos back to Taiwan. The reason he wrote was

bad peformance because of decentered lenses. The vendor was not able to fix this problem.

I remember that the 132mm f/7 William was announced by William as "designed by TMB".

T.M.Back too designed the 130mm TMB signature series f/7 Triplett Apo. Some of the

owners reported too problems due to decentered lenses.

See the spherochromatism curves of the TMB 130 SS in that report:

CN Report: TMB 130 Signature Series - CN Report

And here the William 132mm Triplett spherochromatism curves:

http://www.williamoptics.com/telescopes/images/flt132_chrom.gif

It looks pretty much the same. Both designed by use of Zemax optical design program,

both with FPL 53 glass. Both made in Taiwan.

Both are 3-lens air-spaced desings. So they need spacers. And these metal spacers

are good, much better than a ring of plastic, but the cell should be designed so that

they do not get into the light path.

The lens diameter should be some millimeters bigger than the claer aperture.

1) the spacers di not get into the light path

2) the llens edges tend to be turned down, and so they are hidden by the lens-cell

3) and so the lens deges nedd not be blackened

When CaF² cristal lenses or fluorophosphat glass lenses are used the lens-cell should

be temperature-compensated. They change a lot with changing temperatures,

and the cell must support the lens without pinching the lens.

It is not easy to set up an optics that is both optically and mechanically top.

A good friend of mine told me that his TMB (made by LZOS) shows astigmatism when

he takes the scope out from his home into cold wheather. The lens-cell cools down

much faster than the lenses do. After some time the astigmatism vanishes.

Sorry for my limited english.

Regards, Karsten

[Darth Takahashi]

No thats a great response Karsten, isn't there a german guy testing the hell out of all these so called top class telescopes?

I keep running into a site every now and again but its in the German language so I never book mark it? Anywa,y the reason I ask is that I remember him turning up problems with WO, however the TMB designed telescopes were OK. My question is do you know this site?

It always nice to have independent data to back facts up!

And before anyone thinks I have a problem with WO, I have owned and passed on now a very nice Zenithstar 105. I still own several items including my favorite eyepiece UWAN 32.

Neil.

[GazOC]

This one Neil??

http://www.astro-foren.de/forumdisplay.php?f=199

(Needs translating)

[FLO]

Good to see you posting again Karsten

Is the spherochromatism chart from the original FLT-132 with TMB/FPL-51 or the current WO/FPL-53 model?

That site does look interesting Gaz, I wish I spoke German

[GazOC]

Google Translate

[FLO]

It's going to be a long night

[Darth Takahashi]

Thanks Gaz, that is indeed the website, I'll bookmark it this time. You don't need to read German has numbers are numbers and as Gaz points out either google or babelfish make reasonable translations.

The problem with telescopes is even reasonable ones can make good images of extended objects. You should never buy one based upon the images made by others as there are just too many variables!!!

This guy Rohr performs repeatable scientific optical tests hat cannot be easily disputed, if at all.

Neil.

[ollypenrice]

The WO is clearly a far more ambitious instrument than the Meade-Astronomica one. But is its ambition realized or has some probably trivial error led to these artifacts? How bad are they? My opening post was NOT and attack on the WO scope but on the review. I want to know far more about these artifacts. It struck me as absurd to leave it where they did and this won't be Pete Lawrence's fault. It is an editorial thing.

As for saying the WO scope is 'far better optically' than the budget 127, well that depends on what you mean by 'far.' The 127 could be better; it could have a field that was flatter for further and it could control blue stars better. But whether that's enough to put it 'far' behind the best is a matter of opinion and how you decide to scale the law of diminshing returns. Actually the only scope I have seen down here which I truly would put in a class of its own is the Takahashi FSQ. I would say there was a wider gap between my Genesis and an FSQ than there is between my Meade 127 and a Tec 140. Both scopes are regular visitors here. That's completely subjective... and would I rather have a Tec 140? You bet I would!

We need better reviews!

Olly.

[FLO]

Yes, there is a law of diminishing returns, it is expensive to squeeze the last ounce of performance out of an optic.

The danger with threads like this one is that they usually end up being little more than a discussion where people assure themselves, or others, that what they spent on their own scope was worthwhile. Lets face it, the thought that your telescope might perform as well as one twice the price is attractive and the mere suggestion that one only half the price of yours might actually be as good is scary! Unfortunately/fortunately that is rarely, if ever, the case. Telescopes almost invariably perform according to their price.

As for the review. Unlike this thread it did not focus on only one element of the telescope's performance. IMHO, it is enough that the reviewer noticed and mentioned the artifacts. Those who are concerned can investigate further and forums like this one are an excellent medium for such investigations.

Of course, I could be talking nonsense

[ollypenrice]

Hi Steve,

No, far from talking nonsense you make some very wise observations. I agree that telescopes do, alas, generally perform in accordance with price but there are exceptions, particularly in respect, I think, of quality control. And I also agree about what tends to happen on these threads and suspect I am guilty to some extent of the tendency you mention! I apologize.

But I also feel that BBC journalism has a world wide reputation for a very good reason and should not lose sight of its ideals. When a review becomes a showcase is something of a moot point in magazines.

I was greatly tempted by the WO scope and would like to see more images from it. Likewise from the 158. I like refractors but, by all that's holy, you need to be sure at those prices.

Olly.

[KaStern_Former_Member]

Hello Steve,

I found the curves on this William Optics page:

William Optics - FLT 132 Triplet APO

when I clicked onto "Chromatic Aberration Graph".

The specs given by William Optics are: 3 elements, Air-spaced, FPL-53

As I understand it the graphs are from the FPL 53 Objective.

Greetings, Karsten

[GazOC]

I agree Steve, scopes usually perform according to their price, all you can do it try to pick a nice point that suits you on the price/ performance graph.

[Ant]

If I my throw tuppence into the fountain.

I certainly wouldn't buy a scope / not buy a scope based upon the reveiw in a magazine. There are two many things that are unknowns, was the scope hand picked for the reveiw? We'll never know that one for sure. Is the reveiwer associated with any of the products being reveiwed.

And proably the most important to me is, what pressures are being placed on the magazine from the company providing the telescope to give it a good reveiw.

Are you going to risk 10's of thousands of pounds worth of advertising revenue on a less than good reveiw?

We'll never know.

But at least with Fourms like this one, UKAI and Astrochat we read about real people using these scopes over extended periods of time, we see images taken through them with lots of different camera's. It comes down to the opinion of the many not the one.

Ant

[Darth Takahashi]

My last comments on this subject are as follows;

There are two significant purchases that you are going to make in this hobby and they are listed below in order of priority;

1. Mount

2. Telescope

Where the mount is concerned things are at least clearer, since the characteristic that you want are known. High tracking accuracy with low periodic error, GOTO at least for me was an option (nice to have).

Where the telescope is concerned things are not so clear at all. There are so many different option available from different company for different tasks etc... Over time I have upgraded by telescopes and mount. Although it my appear that I have spent a small fortune on this hobby, I didn't spend it all in one go!

Now to the point, once you have navigated the telescope mine field and made your selection. The last thing that you want to discover is that you have selected a marginal telescope! Especially when it represents a significant part of your budget.

To me the issues with the FLT132 seem to be silly, unless some optical expert want to correct me, it seems additional / slightly bigger baffles would cure this issue, correct? Therefore, WO should action this ASAP.

Regarding the review, which I have yet to read, my S@N will be sent on to me soon. I agree that we need proper repeatable optical test results for such equipment, not the simple statements that are currently made.

Once people have made such a purchase they will most probable keep such a telescope for a lifetime and thats what these reviewers need to understand.

This is my last rant on this subject.

Neil.

[FLO]

... I also agree about what tends to happen on these threads and suspect I am guilty to some extent of the tendency you mention! I apologize.

No apology necessary, least of all to me

Thank-you for the chart Karsten, I had heard that the new FPL-53 optics was very closely related to the TMB design and your chart appears to confirm that.

Sometime I shall search the William Optics user group for images made on the FLT-132 as I have not come across the spikes before so am guessing they are not typical of the design(?)

But at least with Forums like this one, UKAI and Astrochat we read about real people using these scopes over extended periods of time, we see images taken through them with lots of different camera's. It comes down to the opinion of the many not the one.

Definitely

Prior to FLO my purchases were made after consulting SGL and other astronomy forums. There really is no better way to research a product. Even today, most of what FLO stocks is as a result of advice, requests and recommendations made on forums. Its largely why our advertising budget is spent on forum sponsorship and not on conventional printed media.

[Tiny]

To me the issues with the FLT132 seem to be silly, unless some optical expert want to correct me, it seems additional / slightly bigger baffles would cure this issue, correct? Therefore, WO should action this ASAP.

Regarding the review, which I have yet to read, my S@N will be sent on to me soon. I agree that we need proper repeatable optical test results for such equipment, not the simple statements that are currently made.

Once people have made such a purchase they will most probable keep such a telescope for a lifetime and thats what these reviewers need to understand.

This is my last rant on this subject.

Neil.

Speaking of baffles with some of the early versions of the scope where the problem was noticed at least one chap made a mask that blocked out a tiny amount of the edge of the field and the problem disappeared.

[FLO]

I hesitate to post this but a customer has emailed me a couple of links to a site with some superb images. They are relevant because if you look carefully at the brighter stars they show the same diffractions.

Here is one of the links:

Karel Teuwen

If you look at the hi-res version and check the bright stars you will see the diffractions. It takes a while to load so here are some crops:

They are from a TMB 152mm f8.....

I don't wish in any way to appear critical of the telescope or the image, that would be silly, both are absolutely superb. I post this in the hope that it will add some perspective to what has become a slightly skewed discussion.

Puts on tin hat and jumps in bunker:hiding:

[ollypenrice]

Well there's a thing. Karel Teuwen's observatory is a spit from my place. If you want to see astro images...he's yer man.

Olly.

[ngc2403]

if the stars in the review are anything like them then i would be happy to buy that scope. i like that sort of stuff around bright stars, it makes them stand out like the bright stars that they are.

ally